5W30 Diesel Rated Oil

[VT365]

Do you guys see any advantage to using diesel rated oils in gasoline engines? i.e, Additive packages being too harsh for gas engines?

 

[Z-Michigan]

I don't see any advantage. Look for the applicable gasoline rating - probably SM (API) depending what you're putting it in. The diesel rated oils of the latest ratings are either designed for soot control with EGR (CI and CI-4+ oils) or special, pricey additives package to avoid damaging the new diesel particulate filters, along with a similar but not quite as good level of soot control (CJ rated oils). Neither one is likely to make a difference for a gasoline engine. Having changed oil several times on a 2005 diesel vehicle with EGR, the soot level in the oil was incredible, like liquid coal. Gas engines don't face this issue, but do face other issues like fuel dilution (possible in diesel but bigger issue in gas). OF course there are some oils that have both a Sx and a Cx rating - often one of those ratings is much more dated than the other (e.g. Mobil 1 0w-40 with SM/CF rating; good for gas engines, 15 years outdated for diesel engines). If you like an oil that happens to have a good diesels Cx rating, great, but I would focus on the gas rating if you're putting it in a gas engine.

 

[Sully2]

Z-Michigan: I agree completely!

 

[frank_miller]

some cars it would be helpful, so not. Depends..

 

[KICK]

funny thing is the 5w30's that have that starburst sybol (for gasoline engines) are low on certain anti wear additives that tend to foul catalytic converters.

you can infer that a diesel rated oil that also has the desired S rating has more lubricating chemicals than the similar non diesel rated oil but may ruin a cat over a long time period.

 

[frank_miller]

I heard the samething from people (forums) about high ZDDP in gas engine 10+ years ago..

How can oils low in anti-wear foul cats? That is a new one.

 

[KICK]

from what I remember, its one of the Zinc anti wear chemicals that cause the particular problem.

they flash off on contact with hot cylinder parts and end up going out the exhaust.

thats the theory.

you can't deny that there are 5w30 oils out there with the starburst symbol that says " for gasoline engines" and you will notice many owners manuals specify that symbol.

so whats the difference??? the amount of anti wear additives.

seems the auto makers got together with the oil manufacturers about this specific issue.

I'm a sceptic about most stuff but I'm pretty sure I'm right on this one, it aint the BS that it sounds like.

I'm going to see if i can get more info, will post if available.

 

[frank_miller]

Correct, that is ZDDP.

Also agree. But I do not use 5w-30 anylonger, using 0w-20. I would not have an issue using a C rated oil in a gas engine.

 

[DieselPower]

You will usually find diesel rated engine oils in older gas engines or high performance gas engines, both with flat tappet cams. There's a lot of speculation and some studies I have read that show that there is a benefit from the stronger anti-wear additive package (usually a greater level of ZDDP [zinc])in the diesel engine oil when used in flat tappet cam engines. For more modern gas engines I would really see no benefit.

 

[AlanB]

Do you guys see any advantage to using diesel rated oils in gasoline engines? i.e, Additive packages being too harsh for gas engines?

Probably not the track you are going down, but for my house, the advantage is that we have 1 engine oil that we put in all the engines.

Cuts down on the amount of confusion, and the likelyhood of putting an incorrect oil in an engine.

Also lets me keep a decent amount on hand to assist with changes / top-offs.

I used to try and keep all the oils, for all the equipment, in the reccomended viscosities for the various seasons and temps,,,, then found that something like 5-30 gas oil had been put in the tractor

For me and mine, the 5W-40 synthetic Rotella (or similar) covered the bill close enough on all my engines so away we went to one oil. Lawnmowers, tractors, trucks, go kart etc. (the bikes still get special treatment but nobody but me adds to them)