since its an older engine, even though the top end was rebuilt i wouldnt use synthetic in it. the molecules are much smaller and if you have a small leak with standard dino oil youll have an even larger leak with synthetic. if your piston rings let a little oil pass through it will be even worse with synthetic etc.
i wouldnt say if you have high mileage to not use synthetic though. i would say if its an old engine (like yours) i wouldnt use it but in a car thats within 10-15 years it could be ok. although with synthetic oils now you can always switch back to standard dino oil
i woud just stick to using synthetic on a newer car where the gaskets/seals are going to have a less chance of dry rot. my monte has 130k miles and i put standard in from 55k(when i bought it) till about 90k and then blended until just over 100k and now ive switched to a full synthetic.
the 5w30 is going to be a more thin oil then the 10w30. depending on where you live and if you drive it in the cold really depends on what to use. at that though you can use the 10w30 in the summer and then switch in the winter when its around freezing.
you can use the high mileage oil if you want but its going to have more detergents in it, so again id be a little hesitant in using it on an older bottom end.
personally in my '65 i use the Valvoline VR1 10w30 race oil. it has more PPM of zinc then your standard oil that can be bought offthe shelf which is better for the old flat tappet engines and helps with the wear.
its a little more expensive ($50 for a case instead of $20-30) but i only change the oil maybe once a year becuase of the miles i put on it.
|