An interesting side-topic came up in a post about engine knock.

How many of you use 91 octane fuel?

Do you think it makes a difference in terms of engine performance?
...longevity?

I personally am indiretly forced to use 91 octane as it prevents engine knock/check engine light from turnig on.
Kev

The knocking part is something I would check out. These cars don't require 91 octane to perform up to standard. Are you running the correct spark plugs in decent condition? The NGK equivalent for the OE number seems to work very well. Wiring, cap and rotor in good condition helps. You don't mention the year but I believe the timing is controlled by the computer since 1986 - others may have more specific knowledge on this but it is a question to ask. On earlier models there was a vacuum advance so it is necessary to check the vacuum line for cracks etc. Excessive carbon build up will change the compression ratio resulting in knocking. I think that after a certain year a knock sensor was part of the computerized ignition but I don't have specifics, sorry.

In my 1988 245A, with all OE level parts [i.e no rhinestone-tipped spark plugs etc.] my seat of the pants "tests" indicated that mid-grade ⏥ octane] made the car feel a little peppier than 87, but 91 didn't really do anything except cost more. [California fuel]. Car does not knock even with 87 octane at 300k miles. I believe in using one of the top-tier fuels like Chevron with Tectron, Shell etc. because the additive helps control deposit buildup. Google "top tier gasoline" to see that BMW, Honda GM developed the specs to insure emissions performance and longevity. But I think you have another problem related to the ignition system or carbon or vacuum line.

You are probably right. I definitely have something going on with my motor. I have changed the knock sensor and the engine speed sensor but haven't checked the plugs or any of your other suggestions.
However, until I find the culprit using 91 octane fuel has definitely prevented my check engine light to go on.
I think it's been an interesting conversation nevertheless and I appreciate all of your input. More people than I thought use higher grades of fuel and I did learn about some positive aspect of using such fuel. Thanks all!
Kevin

my mpg has increased by about 3 MPG since swithcing to "regular" 87 octane.

maybe it's the cold weather?

HI ALL BRICKSTER`S!

I have read Your comments and interested a lot of just two issues: Those octans, am I right when i presume, that you has different norms RON?? We use MON. Our octans in Europe are between 90-99. In Russian they have 84-87 gas in the country sides, in near highways ,there is modern gas-stations oct 95-98. But if the B23F ( 10.3:1 comp.?) runs perfectly with 87 gas (no oct boosters) what is the ign.timing? Your "super" is 91 ? I think it is same that our`s 98? Our`s VOLVO`s , which are CR 8.6 goes with 95, that is the LOWE`st octane in FINLAND.All cars which has ECU, and IGNITION system cared with the "computer" handles low octanes, just the power comes out fully in the higher octans. EX. if we have BMW M-3 YM 93, it RUNS using 95, but all the 340 hp is available just in 98. That I mean, if man wont to drive recular gas it is OK. In Volvo`s B-230F, fitted an anaemic M cam, there is NOT ANY REASON TO USE ANY HIGH OCTAN GAS. What is more inportant is the engines condition/ tune up. I am surprised, that price differents 10-20 cents to gall makes any spare in whole costs, maybe if YOU drive 30TH miles in the year. Then it is make sense buy a 240 Diesel. I am curiously, how much costs gas and diesel in overseas? We must pay 95 okt pr. $5.90, 98 is p.r 6.1 LITRES. US gall was pr. 3.85 litres, You all can count. So I mean that if I dont care any different`s of octan`s price, why You ? I think that it is MORE IMPORTANT, that You dont need repair engine, or suffer bad driveability. I think, that there is also quality differences in gas in ALL COUNTRIES. EX, some Benelux and French VOLVO`s engines are inside looking SAME condition, what our cars were in 70`s. They have modern OIL`s, so only reason can be in gas. Here in Finland, leader Magazine " Tekniikan Maailma" tests gasolines, when Europeans "smaller" Oil-Companys`came in our market and sell gas pr. 30% cheaper. Results were disaster of those, dirt in inlet valves so much, that the engines, if drive 70.TH KM using that quality, MUST REPAIR. All companies, wich were allready in FINLAND has everything in order, exept few of ESSO`s (EXXON) examples were not satisfaced, but not near of JET`s gas. In now a days situation is balanced, not WORSE gas and no cheap prises.( You must know that OUR BELOWED GOVERNMENT TAKES 70% tax in gas price.) Whatever, wheels are rolling in here, whithout expensive cars, spares and so on. Guess what the cheapest VOLVO costs in FINLAND? Model is S40 1.6l engine. You must forgive me all the language mistakes and I also understands, that THIS IS YOUR FORUM, I am just a visiter, and my intrest`s is not to HURT ANYONE. Just make a communication to all VOLVO drivers around the English speaking WORLD. Especially in USA. I had there far relatives, they had Past Away, and old friends are disappread. Thank You FEW peoples, who has send me POST. IT WARM`s REALLY. BTW: Here is +2C and not a bit of snow. Somewhere in Europe they had a White Christmas, not in most part SANTA`s LAND. YRS: WEBERMAN

Greetings from snowing and blowing Calgary, where it will hit a low tonight of -23C.

Octane ratings in USA and Canada are derived from the Research and Motor testing methods, by the formula (R+M)/2.

A quote from the 1983 Owner's Manual:

"B21F Turbo and B23F: 91 RON - 87 (R+M)/2 unleaded regular.
B21A and B23E: 97 RON - 91 (R+M)/2 leaded, or 96 RON - 91 (R+M)/2 unleaded (premium fuel)"

A bit of math indicates that a fuel that has a 91 Research octane number would have an 83 octane rating by the Motor method, so (R+M)/2 = 87.

Weberman - you would be interested to know that the octane improver MTBE was developed by Neste OY (now Fortum Oil and Gas OY) who recently developed its replacement additive "NExOCTANE", an environmentally acceptable compound. It seems you Finns have some smarts when it comes to Petroechemical Engineering! (and snow tires, and cellphones....)
--
Bob (son's 81-244GL B21F/M46, dtr's 83-244DL B23F/M46, my 94-944 B230FD and 89 745 (LT-1 V8); hobbycar 77 MGB, and a few old motorcycles)

Weberman,Thank you for the information;

Greetings from Sunny San Francisco California 1/3 Km From the Pacific Ocean
At 6:41 PM it is a Balmy 57.9* F, it is Quite Warm here also.

We have special clean burning {oxygenated} blends of gas here in Cali.
They used to put MTBE in our gas,but it escaped from the storage tanks,
and poisoned the ground/water.Now we get 10% ethanol blended gas.
This reduces fuel economy about 10%,so I always use super from
Union 76 with valve treatment & detergent addatives or Chevron with
Techron {detergent} as the 71-145-S, will 'tell' me right away if the gas is poor.
Cr 9.3-1 {B 20 B}
At my corner station,Todays prices for Union 76: /Octane=RON
91= $ 2.92 & 9/10 US Gal Super
89= $ 2.82 & 9/10 US Gal Mid Grade
87= $ 2.72 & 9/10 US Gal Regular
Econo-Gas {cheap brands} @ $ 0.10 less.
Name Brands in good locations @ $ 0.10 more.
91 was as high as $3.15 in summer peak driving season,and Diesel
is now priced as much as super or even $0.10- $0.15 more per gal.
When I traveled to Oregon this summer in the 240 I got 31.9 Mpg
with non-ethanol {Oregon} gas.Over 400 mi for 13 Gal. {@ 60-65 mph}

We understand you perfectly well,as your English is quite good,and it is
great to hear from FINLAND! Speaking of Finland, the Ice Track Drifting
looks AWESOME! I can only dream of such a driving experience.
My ladyfriend has a 1974 Swan 38' sailboat made in Finland,the
workmanship design,strength,and quality of components is
absolutely superior. Thank you Finlandia, SWAN Rules.
Ken

--
White 86-245 DL, M 46, IPD bars & Wagon Overloads,Commando Bumpers,SS Belly Pan & Air Pickup,Straight-Shot EMT Chassis & Tower Braces,Scorpius Alloys,2 Belt No AC Conversion,Black POR-15 No Glare Front End

It's interesting that so many of you use higher octane fuels. I wonder if the general public does as well or whether the data we are seeing is due to the fact that we are enthusiasts and/or gearheads?
Kev

I'm sure you've heard it but I'll chime in:
I've always used high octane on all my bricks.
I never had an engine go bad on me...since 1968.
I get better mileage, smoother running, improved additives, cleaner pipes.
I'm willing to sacrifice the extra 20 cents per gallon.
Hell, I even use Super in my lawn mower.
--
-Cool Volvo- 1982 240 4 Spd OD w/ 246K, 1989 240 5 Spd w/ 237K. Past proud owner of 1966 122, 1968 144, 1970 145, 1972 144, 1980 245

I use supreme in my Lawn mower too, but thats because Honda specifies it for its lawn mower engines.

I have not seen any 240 manual that specifies routine use of high octane for fuel injected models. My 89 manual recommends supreme for hot climates, I assume because the intake air is hotter.

I have used regular unleaded in my 240s since 1983 and I have never had a bad engine or had to replace or clean my fuel injectors. Most normally aspirated redblocks around here go for scrap metal, not because they are worn out, but because there is no demand for them. The engines usually outlast the cars.

I've used 93 octane for as long as I can remember. My mileage has been as high as 34 MPG on straight highway driving at 60 MPH. And the engine purrs like a kitten, not missing a beat. The only time I have pinging is when I'm in a low gear going up a hill, which means I need to downshift anyway.

When I first got the car, I used low octane gas but had frequent pinging problems then. Not anymore.
--
Mike F - 1984 244 DL - 261,000 miles
Original engine, transmission, drive train, alternator, starter
Undergoing reconstructive surgery with POR-15

Used 89 or 91 due to knock ... until recent T belt change. Now using 87 with no knock and plenty of power.

That's odd. Either something was off before or it's off now. With either the cam timing or the ignition timing.
--
'63 PV544 rat rod, '93 Classic 245 + turbo

Agreed! Ran good before but actually a little more torque now and no sign of ping or crackle on the hills. Maybe the shop cured it by relacing the flame trap. This just occurred to me.
Thanks

I use 91 octane in mine. Anything less and I get pinging (my boost is at 15 psi, with suppoorting mods).
--
'63 PV544 rat rod, '93 Classic 245 + turbo

I have always used premium since I bought the car new. The manual said to, and so did a trusted mechanic. The price difference is not more than a couple of dollars at most- it is worth it. I guess that it is habit- when the car was new I wanted to take good care of it.

See sig line below...everything runs fine on 87, no problems.

The 83 used to ping when pulling hard, even on 91. It has the B23F with 10.3 compression ratio, but the book says 87 is the right stuff. I had to pull the head to retrieve a dropped piece of wire into an intake port, and used the occasion to get the injectors cleaned and flow balanced, decarboned the combustion chambers a bit, adjusted valves and set the timing to the 12deg spec'd on the emissions label.

Since then no pinging on 87 octane, slightly better fuel economy.
--
Bob (son's 81-244GL B21F/M46, dtr's 83-244DL B23F/M46, my 94-944 B230FD and 89 745 (LT-1 V8); hobbycar 77 MGB, and a few old motorcycles)

My '91 pings on anything less than 91 octane.
My '90 ran just find on any grade.

My BMWs will run just fine on anything, but they seem to run quicker the higher octane I feed them.

I run 91 in everything, just to keep it simple.

Costs are $2.67/$2.77 right now in California. That is a 3.7% cost differential. that means I need to get 1.05 mpg better gas mileage to offset the difference in fuel cost between low grade and midrange. I have never cared enough to test it, because you really need to run about three tanks per fuel under identical driving conditions to get a good comparison looking for that small a difference.

Perhaps some of the brickser supercommuters could test that for us??

I use it occasionally and mix it with lower octane fuel. I can feel a "seat of the pants" improvement in performance, acceleration is just a bit crisper.

I'm surprised that so many frugal 240 owners will waste extra $$ on higher grades of gasoline. I have had no problems ALWAYS buying the lowest grade for my 240s, 850 turbo, honda accord, Ford E150 etc. I would appreciate it if someone could post reference to a definitive test proving that the extra octane cost results in higher MPG. I think that claim is along the lines of an urban myth. I tried that myself (compared mileage between grades) and couldn't detect a bit of difference. Certainly not enough to cover the 10 to 20 cents per gallon ($2 to $3 per fillup).

i wouldnt run low octane on a turbo charged motor.

Low octaine is ok for the b21fts set at stock boost. The compression ratio is so low in those engines they don't knock with regular. The manual even specifies regular.

HI JESSIE!

All turbo engines must have low CR ,or we cannot use high boost of charcing. WE can compensed that if ECU turns ingnition after TDC, but then we loose power. Ex B-23ET has cr 9:1, but cyl head is hipo core 405 ,and the cam is B. That why it pulls quite well power without low boost. All F engines has quite low cr and mild cams/ ign program. If we take ex B-230F, and chance cyl block to 531 core, take anaemic M cam out and put VX there. Plus chance rear muffler turbo`s OEM. We get out 136 hp instead 106. Also torque line stays straight between 3600-5600 rpm. Fuel economy stays same,or even drops. This was OEM tuning serie, and warranty stays, like all R-Sport parts. Those A,K and E engines has cr 10-10.5, and them works just high octan gas. Basic times are 5-7 dec. Volvo has several different distributors for different variants. Them are sold only Canada,not in USA.

YRS: WEBERMAN

i am sure i can find more specific, scientific information if i search harder.



but since you asked:

http://www.pelicanparts.com/bmw/techarticles/Borrowed/mult_gas_faq1.htm



here is a small quote from the lengthy article:

4.12 Are brands different?
Yes. The above specifications are intended to ensure minimal quality
standards are maintained, however as well as the fuel hydrocarbons, the
manufacturers add their own special ingredients to provide additional
benefits. A quality gasoline additive package would include:
* octane-enhancing additives (improve octane ratings)
* anti-oxidants (inhibit gum formation, improve stability)
* metal deactivators (inhibit gum formation, improve stability)
* deposit modifiers (reduce deposits, spark-plug fouling and preignition)
* surfactants (prevent icing, improve vaporization, inhibit deposits,
reduce NOx emissions)
* freezing point depressants (prevent icing)
* corrosion inhibitors (prevent gasoline corroding storage tanks)
* dyes (product colour for safety or regulatory purposes)

During the 1980s significant problems with deposits accumulating on intake
valve surfaces occurred as new fuel injection systems were introduced.
These intake valve deposits (IVD) were different than the injector deposits,
in part because the valve can reach 300C. Engine design changes that prevent
deposits usually consist of ensuring the valve is flushed with liquid
gasoline, and provision of adequate valve rotation. Gasoline factors that
cause deposits are the presence of alcohols or olefins ⎺]. Gasoline
manufacturers now routinely use additives that prevent IVD and also maintain
the cleanliness of injectors. These usually include a surfactant and light
oil to maintain the wetting of important surfaces. Intake valve deposits have
also been shown to have significant adverse effects on emissions ⎻], and
deposit control additives will be required to both reduce emissions and
provide clean engine operation ⎼]. A slighty more detailed description
of additives is provided in Section 9.1.

Texaco demonstrated that a well-formulated package could improve fuel
economy, reduce NOx emissions, and restore engine performance because, as
well as the traditional liquid-phase deposit removal, some additives can
work in the vapour phase to remove existing engine deposits without adversely
affecting performance ( as happens when water is poured into a running engine
to remove carbon deposits :-) )⎽]. Chevron have also published data on the
effectiveness of their additives ⎾], and successfully litigated to get
Texaco to modify some of their claims ⎿]. Most suppliers of quality
gasolines will formulate similar additives into their products, and cheaper
product lines are less likely to have such additives added. As different
brands of gasoline use different additives and oxygenates, it is probable
that important fuel parameters, such as octane distribution, are slightly
different, even though the pump octane ratings are the same.

So, if you know your car is well-tuned, and in good condition, but the
driveability is pathetic on the correct octane, try another brand. Remember
that the composition will change with the season, so if you lose
driveability, try yet another brand. As various Clean Air Act changes are
introduced over the next few years, gasoline will continue to change.






--
Enem cam, adj. cam gear, new head, trans & oil coolers, stainless brake lines, cross drilled rotors, e-fan, braces, IPD sways, 100% poly, Bils, boxed front & rear arms, lowering springs, FWD rims, 25/32mm adapters, powder coated stuff, & more.

Thanks for the info. I haven't read the whole thing yet, but I am sure there are differences between brands and additives.

My main questions are: from the same gas station, does the higher octane gas give measurably better mileage? and if so, is it enough of a difference to cover the extra cost?

I think the answers are "No" and "No", or maybe "Yes, slightly" and "No". But not Yes and Yes.

But hey, I've been wrong before!

well, several minutes of searching revealed tons of information both pro & con.

just like oil discussions on bobistheoilguy.com have people touting the cost to benefit ratios of dino oil vs. synthetic oil, the usage of a certain type of gas is usually a personal thing not backed by any science.

however, there is science that backs claims of small increases in milaege, cleaner valves & intakes, better emissions, etc.

you are a smart guy & what you relate has validity.

and, like everything in our culture, we have many choices.

super unleaded is a choice i make because i KNOW it is more refined (w/ aamoco ultimate being the best gas in the States because it is the only gas that comes down any pipeline, in any part of the USA, all by itself).

i appreciate the idea of saving a buck and, you are right, on some level gas is still gas.




--
Enem cam, adj. cam gear, new head, trans & oil coolers, stainless brake lines, cross drilled rotors, e-fan, braces, IPD sways, 100% poly, Bils, boxed front & rear arms, lowering springs, FWD rims, 25/32mm adapters, powder coated stuff, & more.

from what i have seen.
a car using premium had much cleaner valves.
i surely can not use low octane in my 240 turbo at 14 psi.
buy whatever works for you.
thats what i do.
good luck
mike

Ancient conventional wisdom:
If engine knocks on lower octane, feed it higher octane.
If no ping, you can stay with the cheap stuff.

Volvo LH technology:
Base timing has a good amount of advance.
When knock sensor detects knock the computer RETARDS the timing.
When timing is retarded the performance drops but there's no knock or ping.
(Notice I said "WHEN", not "IF".)

We old timers who used to adjust timing at same time as most tuneups know from experience what happens when you retard the timing. RPMs drop right down with the reduction in advance. Want to make a sad car pepper? Increase the advance. Just don't step into the pedal too hard, it will ping. Want to guarantee no ping? Retard the timing, but tolerate the boggy acceleration.

We're blessed with modern technology that lets the computer start at maximum reasonable advance - and then retard as needed when it pings. If you put in low octane gas it will retard the timing any time heavy demands are placed on the engine. It won't knock or ping, but it won't zip either.

Suit yourself.
--
Sven: '89 245 NA, 951 ECU, open-front airbox, E-fan, 205/65-15's, IPD sways, E-Codes, amber front corner reflectors, quad horns. Wifemobile '89 245 NA stock. 90 244 NA spare, runs.

I normally run 89 octane, naturally aspirated 244 that gets a good daily driving.

The last two tanks I've put in 87 octane, no ethanol and I've noticed my MPG increase by about 2mpg with the 87... it's wierd considering my foot is of the lead variety too.

Doesn't ping, at least I haven't noticed it ping before knock sensor does its work... I haven't noticed really any change in power at all (still fairly slow)

Run 89 (bottom of the barrel) BP stuff, no knock, no problems. On a hot day in summer, if I hammer the throttle, the engine gives off one or two knocks and then compensates. In that respect, higher octane should result in higher power outputs.

jorrell
--
92 245 245K miles, IPD'd to the hilt, 06 XC70, 00 Eclipse custom Turbo setup...currently in pieces

I use 93 octane always.Mostly the difference between the lowest and top grade is 20 cents,for a tank full, less than price of marlboro lights and this investment is for good. I also use STP complete fuel treatment after 3-4 months.
Regards
Gopesh

91/Union 76 only,I have been told lower grades are a
false economy,as more fuel will be used to achieve
sufficient power.
Ken
--
White 86-245 DL, M 46, IPD bars & Wagon Overloads,Commando Bumpers,SS Belly Pan & Air Pickup,Straight-Shot EMT Chassis & Tower Braces,Scorpius Alloys,2 Belt No AC Conversion,Black POR-15 No Glare Front End

can you remember when (not long ago) regular unleaded gas was well over $3.25 per gallon?

right now, super unleaded seems really cheap in comparison.

since the price difference between grades is minimal, i bet you barely save pocket change by going cheaper on a fill up.

i run super. always have. always will.

my 240 loves me for it.

cheap insurance. no ping. good performance. slightly better mileage.

my only issue is trying to find a station that sells top tier gas (w/o 10% ethanol) near my house.




--
Enem cam, adj. cam gear, new head, trans & oil coolers, stainless brake lines, cross drilled rotors, e-fan, braces, IPD sways, 100% poly, Bils, boxed front & rear arms, lowering springs, FWD rims, 25/32mm adapters, powder coated stuff, & more.

I use alot for fuel treatments,I like red line/FP-60,Sometimes I use 93 octane. I find by useing fuel treatments,this helps keeps everthing clean,Allso with the mix of ethanol- blended gasoline,you need put back lubrication in your fuel.Even an higher octane wont put back this lubrication back in to your fuel.With these older Volvos the fuel pumps need these lubrication.

I use the low octane fuel in my '86. I do my tuneups every 25K miles and every 2500 miles when I do an oil change, I add a bottle of Techron to my fuel tank and have never had any problems with fuel related issues.
--
'86 sedan with 355K miles with original engine and automatic transmission

I started using 93 about 4 months ago.
--
...
'92 245, Black & Tan, Virgo Mags, 130K