5w-20 Synthetic Oil In Flat Tappet Engine

[Gary Allan]

Jim brings up some good points. While I have run 0w-10 for over a year and 10k in my 2.5 flat tappet jeep, it was a (e)SL additive package. I think my valve springs are somewhere around 200-220lbf max and 70-80lbf on the seats. Nothing to get excited about at all. I don't even have the breathing available to float the things if I tried.

Now I'd do it ..but I'm of the belief that time will destroy this type of engine before anything else.

 

[Christian_89LSC_96XJR]

I saw reduced bearing wear when I switched from Mobil 1 10W-30 to Mobil Delvac 1 5W-40 on a 5.0 HO (302)engine. Lead in particular dropped from about average (according to Blackstone) to 1/3 to 1/4 of average. So the main and rod bearings appear to wear less with higher viscosity/HTHS.

This particular engine (roller cam'd) is also at 1/3 to 1/5 of the iron PPM of the average 302 (I think they are averaging roller (like my 5.0) and flat tappet cam engines)

No change between the Mobil 1 10W-30 and the Delvac 1 5W-40 with regards to iron wear. At least one case where Mobil 1 did not generate excessive Fe PPM readings...

I never tried a 20 weight oil - and from the above findings, I'd be hesitant to do so - I don't want to pull the bottom end apart to change bearings...