I know this one has probably been beaten to death and I realize everybody has their own opinion about what is best or more economical. I don't have a point of view on this issue because I know little about it. I have been using 91 (best you can get in California) for fear of hurting the engine. But this usually ends up costing me about $1.80-1.90 a gallon. I don't mind springing to synthetic oil or ATF. But premium over the next 100000 miles will cost me an extra $1000.

I would like to get a comprehensive survey of other 960 drivers and the experiences you have had with different grades of gas. Power, mileage, any strange noises or failures directly related to gas quality. Does the air temperature affect octane requirement?
Thanks for you imput.
Justin

Interesting discussion Bricksters. I have now at least tempered my strict adherence to premium, and may dip into the midgrade range as the price of fuel begins to skyrocket and the difference between grades increase. Our premium is now at $1.81; a 20 cent a gallon increase from less than a mnth ago. Thank ya GW.
--
John Shatzer, '97 V90 @ 105K

i primarily use 87 octane and today i reset the trip odometer at 357 miles and the light was not on yet.i usually re-fuel around 300 miles.i do occasionally add a bottle of fuel system cleaner.i've had no problems with the 87 octane.
--
83 242 DL -120k, 92-965-167k, 94-965-188k, 83-242 GLT-Gone, but not forgotten,83-245GLT-1'st one -the 1'st 3 currently on the road

I run premium in both my 855T and 745 NA. I run both of these cars hard and mantain them to the letter. They have never let me down. I don't think you would notice any difference running the cheap stuff out to 150K, otherwise there would be more dead Volvos out there. The knock sensors much be protecting the cheapskates.

In the winter, I use a blend of 87 and 89 and she runs and starts fine. I live at sea level and the roads here in Vancouver are so congested there is little opportunity to put the foot down and use the horsepower at the top end of the specrum where high octain is necessary.
Milage in the colder weather has dropped to 20mpg Can, vs 23 in the summer when I run 89 to 91 due to the hotter weather. If I am going for a freeway trip esp in the mountains, then I run 94 octain and it does seem to have more power and I can actually break 30mpg Can which is not bad for a 3500lb car with an automatic.

Interestingly, when I visited Germany,where they all dive really fast, everyone uses 91 to 94 octain as they say their motors last longer as the spark is hotter and fewer deposits are left inside the motor!!

The FAQ section gives some tips on avoiding the lawn-mower no-start problem with 960s. It includes the text:

"A strong contributing factor is excessive fuel system cleaning additives. I know this flies in the face of what has been said loudly and often for the last few years but it is the truth according to a recent study on this very no-start, low compression problem. The additives used for fuel system cleaning make the deposits on exh valve stems worse. If you don't have a fuel system problem with symptoms then don't add anything to tank in the form of a cleaning additive.

Premium fuel has lower volatility and is harder to ignite in cold weather. This can make engine not fire as strongly on initial cranking and less than stellar starting performance give the "lifter" pump-up problem time to occur. "

I've had the no-start condition twice. Since then I've been using synthetic oil and low octane gas and haven't had any more problems.

Robert

Robert,

When you say "low octane", do you mean mid-grade?

DEWFPO
--
1998 S90 066,800 and 1995 964 150,200

I'm using 89 octane without any apparent problems. I assume I would hear pinging, especially on acceleration, if it were a problem. I guess the ECU takes care of the timing under those conditions to prevent pinging.

I did find it curious that the FAQ recommends against fuel additives because of the lawn mower syndrome, especially in light of Spooks explaination of how various gasoline brands comprise a witch's brew of chemicals that could leave deposits in the fuel line, fuel pump, and injectors. So what do you do? Use additives to prolong the life of the fuel pump, or skip them to prevent the no start condition when you move the car to get the mower out?

Robert

Dear Robert

Good p.m. I don't need to move the car to get the mower out. And, when I do need to move the car out of the garage for maintenance, I release the brake and let the car roll backwards, out of the garage. In that way, I can start it up to return it to the garage.

For those, whose driveways slope towards the garage, I'd suggest letting the car sit for 1/2 hour, before trying to re-start. That is, start mowing the lawn, and when you take a break, then put the car back into the garage. By then, the fuel system will have re-set.

I use Techron on the advice of my mechanic, who has decades of experience with Volvos. So far, he's not steered me wrong (pun intended).

Yours faithfully,

spook

The control system for the car contains two knock sensors and the algorithm in fact keeps the engine running at the edge between knock and no knock. It primarily does this by altering the ignition timing.

I've experimented with milage and acceleration runs to see if there was any difference between 89 and 93 the two upper ratings available at the Mobile station I use. NONE FOUND!

I use the 89 most of the time. If I'm going to be pulling my boat trailor on a hot summer day I will treat it to 93.

In fact, with the issue raised, I think I'll try the 87 cheap stuff!
--
'96 965 with 16' wheels at 112K. Had '85 745 Turbo Diesel for 200K.

Dear tjts1,

May this find you well. A key difference between gasoline grades is the amount of detergents/gallon: the government only sets a minimum level.

These chemicals keep fuel system surfaces from being coated with performance-degrading paraffins (waxes) and their carbon-rich combustion residues. These performance-degrading chemicals and residues vary widely for the same brand over time.As detergents are expensive to produce, manufacturers add more to the higher-priced grades of gasoline, and boost the price accordingly.

While we think of chemical products as being pure - i.e., household bleach has 5-6% sodium hypochlorite and 94-95% water (and nothing else) - gasolines are chemical cocktails. Their key commonality is the octane rating.

The octane rating of a gasoline tells us its knock resistance, or how smoothly it burns. The octane number is based on a comparison of isooctane (2,2,4-trimethylpentane) and heptane. If isooctane gets a rating of 100, because it burns smoothly, then heptane gets an octane rating of 0, because it knocks badly.

Gasolines contain a variety of hydrocarbon molecules: most are alkanes with 4-10 carbon atoms per molecule. Gasolines also contain smaller amounts of aromatic compounds (aromatics are ring-shaped compounds, e.g. toluene), alkenes and alkynes.

In short, when we buy gasoline, we're buying a product, with widely varying contents. These will depend on the nature of the raw material. Crude oils vary widely in terms of their content of sulfur, paraffins, metals, etc., and refineries accordingly can process limited ranges of crudes. Most of these compounds will be removed by refining.

Thus, while the car may run fine on a lower octane fuel, the lower amounts of detergents/gallon in regular versus premium likely mean a slow build-up of these residues on fuel system working surfaces.

The way to combat this build-up - which can degrade injector performance among other impacts - is to add detergents. Techron - and similar products - remove gasoline residues, and keep clean fuel system component working surfaces (pumps, injectors, fuel pressure regulator, valves, pistons, etc.)

In short, feel free to save money on gasoline - so long as it does not degrade engine performance - but do not neglect to give back some of your savings to your car, in the form of additional detergent.

Add the detergent to the tank before you fuel, once every 1,500 miles or so.
Over 100K miles, a 12 oz bottle of Techron @ $5.99, will cost about $400. If the cost of premium gasoline over regular is $1,000, you're still $600 ahead. Y


Recent posts show how hard it is to change fuel pumps. Thus, the money spent on extra gasoline detergency would seem to me to be money well spent. It will save you on parts, time, frustration, skinned knuckles, etc., etc. Sounds like a good trade.

Yours faithfully,

spook

I have a 95 960, and always use regular, lower octane gas, no problems whatsoever. I will only buy gas from reputable companies to avoid dirty gas or lousy pumping equipment. My brother is a chemical engineer with an oil company, and he has shown studies that clearly show that while one receives a marginal increase in mileage and power, using regular has no long or short term deposit or adverse effect on a car engine. Consiuder it like bottled water vs tap water from a good area. it tatses better and may have been filtered, but it doesn't kill us to drink from the tap. Save you money and spend the savings on synthetics. FWIW.

I've been running my 96 965 on regular unleaded with absolutely no trouble. No loss in performance or mileage. My owner's manual states that while premium is preferred, the engine is designed to run on 87 octane.
Richard
--
86 740T/87 745GLE/96 960 Wagon

We ran premium on the car for about the first 140K miles or so. Decided to try midgrade and guess what? No problems. No knocking or pinging whatsoever. So far, she's running fine on 89 grade for the last 23K miles. Saves about 10 cents a gallon over premium in my area.
--
97 S90 with 162K miles still going strong

Premium, almost exclusively BP/Amoco Gold...but we'll see if the predicted price reaches $3/gallon this summer! Trouble is there is usually very little difference in price between mid-grade and premium, and if your $1000 estimate over 100K is close, I would argue that's not a high price to pay for such a car. Most six cylinders that I've every looked at requires premium fuel. Hey, but that's just me....
--
John Shatzer, '97 V90 @ 105K