my mechanic used diesel engine oil 15w-40 on my newly overhauled engine and he told me it's ok to use it on gasoline engines. since he's one of the mechanics in a racing team here in my country, he said they use it on their race cars as well and they use a straight 40 weight.

are the components of the two oils the same? will it have any negative effect on gasoline engines?

 

hmmmm well the diesel oil may have more detergents in it becasue diesel engines run dirty, it also may stand up better in the long run but who knows really couldnt tell you thats just my two cents

 

Jeez,

Now I can stop buying that expensive Castrol Syntec.

 

Absolutely, listen to your mechanic instead of the engineers designing and spec'ing out what lubrication properties an engine oil needs. Diesel engines are a very different breed from gasoline engines, and as such need specific lubrication properties. In other words, use diesel oil for diesels, and regular motor oil for gasoline engines. Anything else is stupid. Regardless of what your mechanic says.

 

Your engine will be fine. It is a 15 weight oil that protects like a 40 weight. It is a bit heavier than 10w30, but nothing that will cause engine damage. I have used it in an engine with higher miles to kind of make up for worn parts.

 

might have been for break in.

 

Interesting reply texan! I have had very different experience in practice.

I have three large turbo diesels (Ford 655 backhoe, Case dozer, White triaxle dump) one small Yanmar 3 cyl NA diesel in a mower, 2 GM cast iron Vortec 5.7 liter, 1 GM POS 4 cyl, gas Ford 4000 backhoe/tractor, sold a year ago a GM truck cast iron 5.7 liter..., forgot a couple of gas ford 1 ton dumps over the years......

I use the SAME oil in them all in the winter. Shell Rotella T 10 W 30....thats a diesel oil. In the summer the turbo diesels get Rotella T 15 W 40, the others stay with the 10 W 30. I have been doing this for 20 years. Never touch the diesels.....perfect lube behavior.

I buy my GM trucks new, so I can direcly compare results as I have been buying them since 1978 and running them all over 200K miles. My first GM ran Kendall, the rings siezed at 110 K miles and it started to burn oil, I swithched to Shell Rotella T 20 years ago because I was disgusted with that performance! The next GM truck with a 350, which I sold with a little over 200K miles on the small block had never been touched, burnt NO oil, and had the SAME hot oil pressure it had the day I drove it off the lot.

I WILL NOT generalize to high reving Honda's however.............. But for diesels and cast iron domestics I love Shell Rotella T! The detergent package is robust, and the oxidation resistance of the oil is supurb. I would NOT introduce this oil into a high mileage, caked up dirty engine. It can break a lot of crud loose in a very short time.

As always, just my experience, YMMV.
Regards,
BigMoose

 

you can used diesel oils for your gas motor. for instance on the pennzoil long life bottle its says for heavy duty use in diesel and gasoline motors although long life is known a s a diesel motor oil.

anyways, i wouldnt use a 15w-40 in my honda because i think the 40 wt. oil is a bit high for honda motors. id stick with a 30 wt. oil.

 

Actually Big Moose, Rotella T is suitable for gasoline engines and as such has the required API certification for said duty. More and more diesel lubricants that are synthetic based are now approved for both diesel and gas engines, but my point was in regards to a specifically diesel engine oil (which I should have made clear). If it's not API rated to be used in a modern gasoline engine (meaning SH or better), there's a reason for that. It's not designed for use in your engine, and as basic API recommendations go should NOT be used in it.

 

No sweat! Always enjoyed your posts and found them very informative. Thanks for the clarification.

Regards,
BigMoose

 

there is no difference between diesel engine oil and gasoline engine oil. diesels just use a heavier oil than many cars.

 

texan, so you're saying if the diesel oil has a rating of SH or better then it can be used on a gasoline engine?

by the way, are higher the number of weight the thicker, like 40 weight is thicker than 30 weight?

 

Yes. SJ is the current standard, Sl is the next in line and what many of the best oils are claiming to satisfy.

Yes, higher numbers denote higher viscosity. The vast majority of oils are multi-grade, and give you two numbers because they are rated at two different temps. The first denotes cold viscosity, the second is normal operating temp viscosity.

 

ok.

thanks for all the replies.

 

The S-something (SF or SJ or SL or S??) rating is for Spark-ignition engines. The other rating is C-something for compression-ignition engines. Obviously, its possible to make an oil that meets BOTH specs... Make sure you use one that meets the spec for your engine, if it meets other specs as well, that's OK.

 

Oh really? You may want to do some serious research before believing that. Just a suggestion.
For the rest of the topic discussion:
That is correct Rotella is certified for both gasoline and diesel use. I also agree that using a strait diesel application lube oil is not a good choice due to the diferences in the addative packages. Strait diesel oils are indeed formulated to break down deposits (primarily soot - by product of diesl combustion) and suspend then in the oil. Putting Rimulla oil in a gasoline engine would be an example of a bad choice. This helps remove more soot deposits in the filter and during oil changes. This is the nature of the diesel beast.

Also remember that diesels are more temperature dependent (for combustion) than gasoline engines. Diesels don't have spark plugs.......and some don't even have glowplugs.


[Modified by SLPR, 8:44 AM 2/27/2003]