Opinion: oil change help/input

[TrevA6]

Hi all,

I've got a 94 s4 and am due for an oil change, I have a friend with the same car and he said to use Mobil 1 98HM64 Turbo Diesel Truck 5W-40 Synthetic Motor Oil because thats what he puts in his 911 and his s4. I went to the mobil 1 website and put in my car and it told me to use
Mobil 1 synthetic 0W-40. I don't know if my friend is fucking with me or if it's actually got any worthwhile benefit to use the diesel oil?

What would you do? any input is greatly appreciated.

thanks

[Corrado_Guy]

It really depends on where you live as the type of oil you use can vary from place to place. Typically these cars use very thick oil when compared to other cars so see what the factory recommends, this chart is for the 1995 but it should be same for yours...



If you want an oil that will go all 4 seasons then use 5W/50 and using the above chart you can see it works on all ranges. Germans are cheap and when VW/Audi designed this motor it was designed to work as a gas or a diesel just like the 16V, 8V, G60, and the VR6 and they all use heavy oil. These motors use big clearances internally and they need the thicker oil otherwise your crank could float around and hit the bearing surfaces under high load. Heavier oil creates higher oil pressures and temps but it is what the motor needs and should be in there. There is also a warning in the manual about not doing extended highway driving with 5W/30 installed.

Back in the day when I worked at VW/Audi we used to put 20W/50 in all of the cars we sold with the exception of the diesels which got diesel spec oil (I forget the weight though). I don't know if there is an advantage of running diesel oil in a gas motor, it is designed for the most part to work while having a lot of diesel fuel mixed in with it. Diesels have a lot of blow-by when cold so after the first start after a change the oil is pretty much black.

Personally I would stick with oil that is designed for a gas motor and I would tend to stray towards the thick end of the scale. On my G60 & VR6 I run either 5W/50 or 20W/50 all year long but we don't see much under -10 C so I don't really have to push it. The way oil has changed over the years but the grade of oil has not so you should look at the temps the car will see and pick an oil that fits. Column 'A' are the energy conserving grades and column 'B' are the recommended grades for the motor so look at column B.

[TrevA6]

I live up in Vermont on a mountain, so the car will see probably between -20 and 100 farenheit. So by that chart looks like 5w-50 would be the best choice
for me. Thanks, i appreciate the help.

[TrevA6]

i guess the reason for using turbo diesel motor oil was the higher detergent level will keep the engine cleaner, anyone know if that is true? and would it be worth it for that reason?

[PRY4SNO]

Diesel motors can take more heat, so that spec. oil lasts for longer oil change intervals when used in t/c'd petrol engines.

Mobil-1 isn't typically a Group-V oil, which means not a full-synthetic oil.

My two cents is to stick with something like a Shell RotellaT or Total Energy9000 for cost/value ratio while using a full-synthetic oil.