Australians wanting to use a full synthetic from Mobil or Pennzoil have one choice of viscosity - 5W-50.

Consider the following-

Eighty percent of our population live in a mild climate on coastal plains. Winter lows of 10 degrees, summer highs of mid to high 30s. A climate with no extremes.

Does the above warrant 5W-50 ?

Pennzoil's website states - 'SAE 5W-50 is formulated to give a thicker film at higher temps,SAE 5W-50 does not meet passenger car requirements for fuel economy'.

Am I correct in assuming the same applies to Mobil 1?

My research has indicated that if an engine is in good condition it can be harmed by an oil that is too thick? Higher than normal pressure may blow gaskets, and increased drag may result in increased wear.

The disadvantages of buying Mobil 1 or Pennzoil Synthetic in Australia would appear to be-

Increased wear,

Possibility of blown gaskets,

Reduced fuel economy,

Reduced performance,

Concern that you are disregarding the manufacturer's viscosity recommendations for all owners of passenger cars sold in Australia &

A reduced bank balance.

The advantages of buying Mobil 1 or Pennzoil Synthetic in Australia would appear to be -

NIL for the motorist.

I'm hoping someone out there can convince me that using the oil I've got stored, 2 x 5 litres of 5W-50 Mobil 1 costing $100, will be in the best interest of my 93 945 b230ft.

Should I keep using it or go to a blend such as Mobil synthetic blend that has a 15w-50 weight?

Can someone try to explain Mobil & Pennzoil's thinking?

Your thoughts will be appreciated. Thanks in advance.

Take care,

John H from DOWNUNDER

Before jumping to conclusions, read http://www.nac.ac.za/~TJVANROOYEN/Lubricants.htm.

George Antony

Hi George,

Tried nac.ac.za/~TJVANROOYEN/Lubricants.htm without soccess.

Am most interested. Could you doublecheck the address?

Does the article suggest 5W 50 is suitable?

Thanks,

Take care,

John H from DOWNUNDER

Sorry it did not work out. I have it in a pdf, if you send me your address I will send it to you.

Basically, it says that synthetics fundamentally differ from dyno oil and the numbers are only guides - you must check the letters. It does not mention 5W-50, only 5W-40 and similar differences, but the implication is that it should be OK. My reasoning is that these companies know what they are doing, and would not want to risk lawsuits with a clearly unsuitable product. Oz is not quite a third-world backwater where you can dump anything.

There was also a comparative test in Oz by some hot-rod mag that found BP's Visco 5000 the best, ahead of Mobil 1. Now, that is, from memory, a 0W-40, and not even true synthetic (hydrocracked base stock against the real stuff). I'll try to dredge up a copy of that too.

That said, I perceive an improvement in cold idle and throttle response even with Mobil's synthetic blend (240GL, 1988 model, bought with 290,000 km in February), and from the next change I'll go whole hog now that I know that the motor does not use oil and does not leak.

George Antony

george.antony@cse.csiro.au

Hi George,

I share your belief that these companies know what they are doing. In my mind that would be maximising profits.

How the marketing of 5W-50 in Australia helps them do that only they would know.I suspect it does not go hand in hand with the Australian motorist's best interest.

This weight is not recommended by the manufacturer of ANY car sold in Australia. Maybe Mobil and Pennzoil know better. I am seeking their reasoning.

My car has been using Mobil 1 exclusively since my ownership. I have used Mobil 1 because of my belief that it was better to use full synthetic, even if it was the wrong weight. The engine doen't use oil, but it blackens quickly, even after 7 oil changes with Mobil 1.

Thanks for your response George. I plan to continue my approaches to Mobil Australia and seek the NRMA's support.

We've just sold an 82 Toyota Cressida and bought an 88 240GL. In the process of baselining it. Next task is to rebush the suspension, followed by getting the air con working. Five litres of Mobil S synthetic blend has been purchased for the next oil change.

Take care,

John H from DOWNUNDER johnhr30@yahoo.com

I know Pennzoil uses a hydrocracked Group III base oil in its US-based "synthetics", blending VI improvers to give various viscosity grades. Castrol is the same. Mobil uses exclusively Group IV and V full synthetics (as do Valvoline, Redline, Amsoil), again blending VI improvers to yield various grades. The 10-30 has minimal VI, the 15-50 more.

Volvo does NOT recommend a wide viscosity range such as 5-50, and you are better off with a 10-30 year-around in AUS unless you are in the deserts. It would be interesting to know why they blend such a range for AUS instead of producing normal 5-30/10-30 or 10-40 grades. BMW in the US specs a 5-40 for its cars, based on a full synthetic formulation made, I believe, by Mobil.

The disadvantages of high viscosity oils are poor fuel economy, greater shear at operating temps, reduced cooling capacity, and use of more viscosity improvers which do not add lubricating qualities.

See the FAQ for more information on oils.

I have contacted our prime motoring body NRMA re this situation and asked them to pursue it. Also contacted Mobil, Pennzoil and KMart.

Thanks Steve. This is the second time you have advised me re this oil weight issue. The first time I searched but failed to find the viscosity you and Volvo recommend. Thought it was better to use full synthetic of the wrong weight than to use a premium mineral of the correct viscosity.

My thinking at this stage is to use the 10 litres of Mobil 1 I have stored, and then switch to a 15w-50 Mobil synthetic blend. Interestingly the Mobil technician I spoke to suggested to do this as he agreed their premium product was the wrong weight. He also agreed that it was not the weight recommended for any mainstream Australian driven car. He had no idea why 5w- 50 was being marketed in Australia, other than he thought it was being made in Melbourne Australia.

Take care,

John H from DOWNUNDER

I recall seeing a post on mercedesshop some time ago that Mercedes-Benz is now recommending the use of synthetic Mobil 0W40 (yes, zero), but that this blend is only available in bulk quantities at the present time.