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Masani
09-21-2011, 09:49 AM
Ok, so simple question. I may have asked this before, I'm not sure. Anyway, for my 92 ST i've been using 10w-30 Castrol GTX. Now, I know there are high mileage oils, but what use in my situation. I have a completely rebuilt head, but the block and it's internals are all stock. I currently have about 216.5K miles, with cold-air intake and 2.25" exhaust. All together with the high mileage should I be using something 20w-50? Or a healthy middle-ground? Daily temperatures here range from 63F to about 86F or so. Just FYI.

Luni
09-21-2011, 10:03 PM
Youre going to get all sorts of conflicting opinions on this.

Most high mileage oils have agents in them to help condition seals. Most of the seals are in the head, so I dont know if Id go with high mileage. Some guys will say your engine is only as good as its weakest component, why did you rebuild the head and not the bottom end?

85gtsblackman
09-23-2011, 02:57 AM
probally bhg, id just use gtx 10w40, i use mainly 20w50 cause all my stuff is old and gets the piss beaten out of em

Murgatroy
09-23-2011, 03:13 AM
I ran Chaos' original engine on 20w50. One day I was buying oil and they didn't have 20w50. I bought 10w40. I blew her engine a couple months later.

Coincidence?

Probably.

But I had been running 20w50 in her for over eight years before that.

When we put the new motor in her I filled it with 10w40, then I discovered the burnt rings. I have been running the cheap Wal-Mart 20w50 in her since.

85gtsblackman
09-23-2011, 03:23 AM
so unless u drive like grandma use 20w50

MrTurrari
09-24-2011, 12:30 AM
No offence to the others and their personal experiences but you should run the weight of oil the engine manufacturer tells you to run. The second number is the most important one though because it is when the engine is warmed up. Bearing clearances are specifically set to the weight of oil they tell you to use. If you run too thick of oil the pressure goes up but the flow goes down. Oil is not only a lubricant but is also a coolant and less flow means more heat stays in the moving parts of the engine instead of going into the cooling system. Also thicker oil is harder to pump and puts a little more load on your engine giving you worse gas mileage and less power. So unless you know your bearing clearances have increased you should be running what they recommend.

The other characteristics like synthetic or not, high mileage or additives can increase the time between oil changes or help seals last longer respectively but are not as important as keeping the right weight of oil in there and topped off.

Masani
09-24-2011, 01:26 AM
why did you rebuild the head and not the bottom end?
I blew a head gasket, and the old head had so much pitting that no amount of machining would prove fruitful, the cams were chipping. Anyway, I had an opportunity to just swap out the whole head for a rebuilt one for a few hundred USD. In any case, this engine just has to last till next summer when I do the 4agze swap.


so unless u drive like grandma use 20w50

Well, for some reason my car has been running in Limp mode or something, never revs higher than 4k or so. I have no choice but to drive like a grandma. This island is so small it's rarely a problem.