15w40 oil

rodgernbama · Jul 10, 2011

I was talking to a friend about oil the other day and he said his cousin had been using the 15w40 oil in all his engines(cars,tractors,mowers etc.) without any problems. I thought this oil was for diesel engines. Has anyone tried it in their gas engines?

Bob · Jul 10, 2011

Yes. The ONLY down side would be in late model cars that have $$$ high-tech, finicky "cats" that can be harmed by the anti-scuff ingredients in the diesel oil.

The engine itself will THRIVE on diesel oil.

tjdub · Jul 10, 2011

I run it in all my gas and diesel engines except my wife's car. I've been doing so for many years without trouble. I'm not going to put it my wife's car though because if it turns out to cause a problem I'll never hear the end of it

As I've understood it, you can run diesel oil in a gas engine, but not the other way around. As Bob says, there may be unforeseen consequences with catalytic converters, but that's not something that causes me much concern.

Anonymous-0 · Jul 10, 2011

Someone who knows posted awhile back that diesel oil is best oil. Think about the conditions it has to withstand. This person said in tests that diesel oil outperformed many racing oils. Due to standards that must be met even the cheapest diesel oil is better then most regular oil.

showcrop · Jul 10, 2011

I think that it was Shell's 15-40 used to be referred to as "All Fleet" in their advertising, because a company needed just one oil for all different types of vehicles.

Bob Bancroft · Jul 10, 2011

Yes. I use it in everything except the car and pickup, which call for an "energy saving" lighter oil.

thurlow · Jul 10, 2011

What do the API specs say on the oil in question? That's at least as (maybe more) important as the weight.

john in la · Jul 10, 2011

The API service rating is what you need to go by not the viscosity.

S rated oil is for gas engines and
C rated oil is for diesel engines
The second letter in the rating such as SN or SM refures to the year model it can be used in.

Viscosity is more what your lowest expected outdoor temperature will be.

Dean · Jul 10, 2011

I use nothing but 15W40 diesel spec oil in all of my engines except late model automobiles/gasoline trucks and small air cooled engines.

Dean

Bob Bancroft · Jul 10, 2011

Do you have some negative experience from using 15W40 in the little air cooled engines? I use it in the tiller and pump(both 5HP B&S) and lawn mower(24HP B&S). No troubles so far.

John Harmon · Jul 10, 2011

Good or bad I use 20/50 Castrol GTX in my car,truck and motor home.Have for a long time. Right now by noon day time temps range from 106-112 Avg. I saw 123 on Interstate 10 down by Sky Harbor Air Port close to down town Phoenix Az. awhile back.Traffic ,including me was moving right along at 65-70 MPH.I guess we don"t pay attention to the heat but I think my vehicles are being taken care of very well with this oil.

Bryan inIowa · Jul 10, 2011

If you run anything other than spec oil in overhead cam ford engines you will more than likely blow a cam follower off .

Dean · Jul 10, 2011

No. I just happen to have a couple of cases of 30W engine oil that I use in small air cooled engines. I'm sure that 15W40 would be fine therein.

Dean

37chief · Jul 10, 2011

I use 15-40 in my diesel tractor engines.This is what happened to me when I used it in my old AC Model M crawler. A piston siezed and actually stopped the motor. I had to tear down the motor and hone the cylinder. It was never the same, finally changed the motor. I use straight 40 wt now in my M's. Stan

sotxbill · Jul 10, 2011

15w-40 hd oils are heavily fortified oils with tons of additives... therefore they work well with most all engines.

The have addtives that fight coking and super clean the engine.

The extreame base additives can and do remove deposits in engines. So.. if you use a modern hd oil in an engine that is totally gumed up, it can cause the sludge to slowly dissolve and break loose from the engine surfaces. in a few rare instances where an engine is coked up at the pistons, the carbon can break loose and score a cylinder. that could be what happend where any modern hd oil is introduced into a serverly gummed up engine.

I use 15w-40 in all my engines except where problems with engine require an ultra special oil. or you can upgrade to 5w-40 hd oil to get even better protection..

Bob · Jul 10, 2011

"A piston siezed and actually stopped the motor."

SOMETHING doesn't "add up" there!

Brian Jasper co. Ia · Jul 10, 2011

Nope. The only reason to not use 15-40 on an overhead cam engine is if it has variable cam timing. The heavier oil slows the reaction time making the PCM unable to control cam timing. If you have a follower pop out, you likely have a sludged up engine and sticky lash adjusters or low oil pressure.

Brian Jasper co. Ia · Jul 10, 2011

Agreed. If oil was the cause of seizure, it was severely dilluted with fuel or water.

Traditional Farmer · Jul 10, 2011

I've been using it in all my engines gas and diesel for years with no problems.

INCase · Jul 11, 2011

It "can be" used in gas engines. As others have mentioned, most diesel oils can be used in gas engines. THere are a few (just a few) gas oils that can cross over to diesels.

HOWEVER I would not recommend 15W-40 in newer (last 3-5 years) gas cars/trucks with cylinder deactivation.

Watch out for the new (2007 and up) diesel truck engines must have CJ4 oils so if you go with one oil across the fleet make sure it compatible with all engines. That's getting harder to do. Generally CJ4 is reverse compatable.

One down side is the higher viscosity will rob some fuel economy and the 15W in the winter will be thicker and not get thru the engine as fast in cold start ups. Some of the newer diesel engines are going with 5W-40 instead of the 15W.

I put straight 30SAE in my tractors and lawn mowers. Cars get AMSOIL 10W-30 synthetic.

15w40 oil

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