I've just rebuilt my suv engine, replaced rings, polished all pistons, machined heads and polished all ports. all new hoses, radiator, all sensors. engine runs really good and quiet.
put initially castrol 20w-50 and have read I should replace at 50 miles, then
500 and then every 3000 milesmany older mechanics tell me to keep engine with castrol 20w-50 or similar and
*not* to go synthetic but won't tell me any real reason as to whyany comments?
yes...
1) is 20W50 the mfgrs. recommended oil for this engine? If not, did you build the engine with looser clearances that would indicate going to a heavier oil? If not, i'd stick with the mfgrs. recommended weight, (although if that is a 5W20 I would seriously consider using a 5W or 10W30 - 20 weight oil just seems to thin for good protection to me. I know, I don't really have anything to back that up, but a 30 weight is as thick as most newer engines are designed for, with a few exceptions.)2) No reason not to go to synthetic, but I'd wait until the engine has some miles on it. How many really depends on how long it takes for it to feel broken in. If it uses oil at first and at some point stops using any oil at all, after that point I'd feel safe switching to a synthetic.
good luck,
nate
Somewhere in the dark ages past, word got around that if you used synthetic oil from the start it would be SOOOO slippery that the rings would never properly seat and you'd have a chronic oil burner.
It might or might not have been true, to some degree. But the Corvette, Viper, and a number of other cars come from the factory with Mobil 1. I switched my freshly built Mopar 440 to Mobil 1 at 1000 miles. I did the initial fire-up on Castrol 10w30 (20w50 is for worn-out engines, not new ones- WAY too thick!). Did the cam break-in run for 20 minutes, changed the oil and filter to get all the break-in lubes and any leftover grits out. Then ran for 100 miles on 10w30, changed oil and filter again. Then at 1k miles, I switched it to Mobil 1 10w30. So far its got about 15,000 miles on it, oil consumption has dropped to nil (or as close to nil as you can get with a big-bore v8), and its running fine.
I'd still tend to err on the side of caution with a home-rebuilt engine, which is what I assume we're talking about here.
nate
There's no good reason. Until conventional oil breaks down, its properties are the same as synth. The only reason for using dino oil is the cost of filling and tossing synth. Use cheap dino for 50, 500, and 3000, and then switch to synth every 10-20K.
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