SAE or Synthetic fluids

[MY1978]

So, my truck has 146,000 original  miles.  I have always used SAE 10-40 - not high mileage.  It has always had a lifter tick.  My dad (a career mechanic) and I tore the engine down to the block, lifters were checked/replaced as needed, magnaflux the heads and then reassembled at 97k - so back in late 80's maybe.  Even after that, the tick remained.  Are there any pro's or con's to using a synthetic?  Also, what about transmission fluid - conventional or synthetic.  what about this "stiction" I have heard about?

[Shifty]

There isn't a negative to using synth's, other than the price.  If your motor is being held together with sludge, synths are good at cleaning, so you may develop a leak. 

The "stiction" thing is for diesels. 

FWIW, I like Lucas 10w40 synth, regular dexIII for trans, Lucas synth 75w90 for the diffs. 

[MY1978]

Thanks for the info.  I use non-ethanol for fuel, so I will stick with the ol' tried and true SAE.  That is what the engine was built to use, that is what I will use until I cannot get it any more.  Just curious since there is so much of the synthetic out there.

[Stewart G Griffin]

i can't help you with the syth vs. conventional as i don't know much about oils, but i don't think there is any downside to using synthetic.   And, as far as the price debate, 5 gallon jugs of  mobil 1 synthetic are (probably still) $22.95 at walmart!    So, the whole, conventional is cheaper than synthetic is really a wash.

Aside from the breaking period, which i used valvoline 10-30, i have only used Mobil 1 synthetic in the 4.3 (which is really a small block chevy with 6 clys instead of 8.


How old is your engine? More importantly, you mentioned lifters.  Do you have flat or roller lifters?
Why do you use 40weight instead of 30?

[MY1978]

My engine us original.  Broke down to heads at 97k which would have been in late 80s.  As far as lifters being flat or rolled, I have no idea.  My dad was taking care of that part while I was busy cleaning up carb.  As far as using 10-40...........my owners manual suggests 10-30/10-40 as it has the widest temp range so that us what I have continually used for 43 years.

[Shifty]

I think you know your answer, go with what's worked so far!  Cheers!

[VileZambonie]

Put this crap in and buy whatever is on sale https://www.stp.com/products/oil-additives/oil-treatment

[ChrisD]

Hi,
I‘ve been told (more than once), that if your engine has run long time with mineral oil and then change to synthetic, it‘s possible, that some seals become leaky because the synthetic oil is more agressive and flushes deposits away.

What do you think about that?

Regards
Chris

[Stewart G Griffin]

Actually, i just re-read your post.   The lifters (which, if the engine is original, then you do have flat lifters.  This in itself is important and we'll get into that in a sec) "were replaced as needed."   But the cam was not replaced?   This, right here could be a big problem.