can i get away with 0w30 oil ?

[instarx]

If the Hayes manual is correct and the manufacturer specified 40 weight oils, then no - it would probably not be OK. But I have doubts about that Hayes manual.

Here are the viscosity ranges of oil weights at 100C:

0W-30, 5W-30, 10W-30, 30
9.3 cSt – 12.5 cSt

0W-40, 5W-40, 10W-40, 15W-40, 40
12.5 cSt – 16.3 cSt

(See my reference below)

As you can see, any 30 weight oil would fall outside the acceptable viscosity range for an engine that was supposed to run only xW-40 oils. There is no overlap. But honestly, I find it hard to believe that no 30 weight oils were acceptable for an engine made in 2000.

I run synthetic 0w-30 in my 1995 6.5L diesel and my 2000 Volvo turbocharged engines year round, but the owner's manuals recommend either 30 or 40 weight oils. (encompassing both ranges listed above). Check an original owner's manual to see if any 30 weight oils are OK to use. If so then you're fine with synthetic 0w-30.

Here is a technical article that shows how the various oil grades compare in viscosity at 100C. Its about Chevrolet Corvair engines but the oil stuff is universal. To see if a 0W-30 oil will work in your particular car, find the grade recommended in the owner's manual. From that oil grade you can determine the viscosity range the engine was designed for. Then see if the new grade of oil you want to use is in the same viscosity range. The chart is on page three. Using this chart for my Volvo, 0W-30 oil works fine from -30C (-22F) to 30C (86F). I should use xW-40 above that, but I don't.

http://www.widman.biz/uploads/Corvair_oil.pdf

This article was found in the Bob is the Oil Guy site which has a wealth of information about oils.

Originally Posted by IndyIan

but in your climate it makes more sense to use 10W30 to me, in general the closer the numbers the longer the oil lasts close to the original specs.

Ian, I do not think this is accurate. I'm no oil expert, but everything I have read about oils indicates that it is the quality of the base oil and the type and amount of additives that determine how long the oil stays in spec - not how close its viscosity range is. A pure synthetic 0W-40 will last longer than a petroleum based 15W-30.

[modmonster]

i put 5w30 in. we'll see how it goes.

[Whoops]

If your going to go fiddeling around with the oil viscosity, I would strongly recommend you put in an oil pressure gauge. The bearings all run on oil-pressure. If the engine is new, then it will have pretty tight tolerances and it will still have pressure, even at idle. If you let the oil pressure get low, then it is bearing surface on steel and it will chew the living daylights out of the bearings in an extremely short period of time. If that happens, then your hosed, no if's, and's or but's.

You can in principle save a small amount on fuel, but the amount you can save, compared to the risk to the engine is a pittance.

[modmonster]

ok

[modmonster]

i've bought the gauge. arrives monday

[modmonster]

googleing corsa 5w/30 is reassuring me.