Ecoboost/Subaru turbo oil...shearing, fuel dilution...

Aug 14, 2019
[Linked Image] The source of this image is Amsoil website. The big issue with fuel diluting Ecoboost engines like the ones in the F150 and the Subaru turbo engines is fuel dilution turning 5W30 into a 5W20. I dont have any data on how this effects the engine, but I have never been comfortable with it. Im happy I found this Amsoil study which I loosely corroborated with my own oil tests on Mobil Delvac 1 5W40. Any of the HDEO oils listed in the study would be good. One thing I might point out is the Chevron is API SN Plus which goes better with turbo gas engines. My next batch will be the Chevron to see how it goes. While the Amsoil may or may not be best oil here the fact is any of the HDEOs would produce a desired result in the turbo direct injected engines. That result is not seeing the oil go into the single digit CST (viscosity) range.
Last edited:
Originally Posted by demarpaint
A lot has changed in 10+ years, unfortunately that graph is meaningless now imo.
Great Point!
The DI dilution is bothersome but a number of theses engines have been around a few years now Always had mixed emotions with the 0w20 in my 5.3L DI V8's … and now with a good stash of Mobil1 AP 0w20 hate to not get some mileage from it. I have lots of $4 PF63E filters that take 5 minutes to change and that lets go of a quart. Thinking 5k on AP, change filter and add a quart of SAE HD30 SN Plus … do 3k more
I would bet every one of those oils has been reformulated in the last 11 years. That chart is meaningless.
NOACK and TBN are missing and it may lend a little more structure of understanding for a good comparison.
Penzoil is missing because I think it doesnt have an HDEO version or it may have it under a different brand name. Basically there are two varieties of 5W40 which are Euro that tends to be a lighter version and the HDEO which is more robust. One is designed for vehicles like the Mercedes S Class and the other for heavy hauling diesel pickups F250 and up or even big rigs. In this comparison its the better known HDEO varieties. What is suspiciously missing is Redline 5W40 but thats ok. Any one of the HDEOs will do except for T6 that isnt gas rated. I know people still use it for gas engines but take note not suggested by Shell. It would be interesting to include Mobil 1 Turbo Diesel Truck and I think that oil is more for F250 F350 diesel vehicles. The Delvac is for heavy duty applications. TDT is Group III and Delvac is Group IV with more manufacturer ratings.
Last edited:
The formulas have indeed changed. Mobil Delvac 1 which I use is a bit thinner than the initial viscosity in the graph for one.
I looked at the current Chevron Delo product sheet. While Delvac got thinner Delo got thicker...
OUTDATED for sure + @ the $$$$ Scamsoil should be better as would other high zoot REAL synthetic oils!!!