TPI86TA

I heard that if you don't use the right weight oil, it can cause your oil pressure to drop. Is this true and what weight oil should I be using for an 88 GTA with a 350 TPI. The GTA has a little over 140,000 miles on it. Also should I use one of those higher mileage oils or maybe also an engine additive and or an engine flush. Also what is the proper oil pressure I should have for my stock 88 GTA with a 350 TPI. Thanks, Al in NJ

RJR99SS

the "proper" oil weight is kind of hard to say, it depends on a few things. Obviously, the heavier the oil you have, the more your pressure is going to drop. Not that that's necessarily bad.

What kind of weather does the car see? If you only drive it in warm sunny weather, 10w-40 or maybe even 15w-50 would work.

If you drive it every day, 10w-30 should be just fine. Maybe use 5w-30 in winter if it gets VERY cold where you life.

I really wouldnt trust the "high milage" type oils, they dont really do anything. Some people call it "designer oil". With 140,000 miles i wouldnt use any additive or flush on it either. The reason being there could be quite a bit of sludge built up in the engine, if you flush it could actually clean the engine out so well that you may clog your oil pickup screen with the junk. I've seen that happen.

I'd just use a high quality conventional oil, with regular oil changes.

IROZINCO

iTrader: (1)

Umm - the heavier the oil, the lower the oil pressure? Actually, the thinner the oil, the lower the oil pressure. At least in my experience! On a higer mileage car, people tend to run a thicker oil. I run 20w50 in the summer and 10w40 in the winter. When I run 20w50, i get 45psi at idle and 60 at speed. When I run 10w30/40 i get 30 at idle and about 50 at speed. I think that GM said 30/55 was about the right numbers. I have an 87 350 TPI, with 125K and it seems to LIKE the valvoline "for higher mileage engines" oil. Of course, once you get over 100,000 on the engine, the main thing is that it HAS oil! Especially if it burns or leaks it! We have very cold winters, so I switch to a lighter weight so I can get oil up in the valvetrain more quickly when it's cold. Conversely, when it's hot, I run a thicker oil so it pumps well when it's hot and doesn't thin out so much. Remember, 1st number on the oil is the 'thickness' or viscosity of the oil when cold, 2nd number is the viscosity when hot. So, if your engine doesn't burn/leak oil and you have good OP with 10w30 which is what GM recommended, go for it and use synthetic if you are so inclined. IF you have leak/burn issues, sometimes a heavier weight will help. If your bearings are going, nothing will STOP them, but sometimes you can get just a bit more time out of your engine by changine the weight of the oil. I wouldn't just throw any old additive in to my oil, but the 'Roc does seem to like the Valvoline hi mileage stuff.

TPI86TA

ok cool thanks.So the second number is the weight or the first number is.Cause i drove this TA and noticed the oil pressure maybe around 15 PSI and it would fluctuate and the guy told me its cause of the 10 weight oil.I just know i wanna put an oil in that will give me better oil pressure.Or is my best bet to put in a new oil pump?

RJR99SS

both the numbers are the weight. Too put it as simply as a i can...

the 10w-30, or 5w-30, or 20w-50, or whatever are multi-viscosity lubricants. They actually "act" like different oil wieghts at different temperatures.

the 10w, or 5w, or whatever is the first part. This is the weight the oil will act like with the engine cold.

The next part -30, -40, -50 is what kind of weight the oil will act like with the engine hot.

There's also regular old 30w oil out there, obviously this oil acts like 30 weight all the time.

25THRSS

15 psi at idle is normal.

RB83L69

Actually, the first number is what the oil actually is; the second number is what the additives make it act like when it's hot.

Normal oil pressure in these engines with the factory oil pump is 15-20 idling and 45-50 cruising, fully hot. Use the thinnest oil you can use that keeps those pressures. Since it doesn't go below 10° very often where you are, I wouldn't go with anything thinner than 10W. 10W-30 should be fine.

TPI86TA

OK cool i was worried about there possibly being another problem with this car im buying.I think the lowest the pressure went might of been was 12 PSI but im not sure,i think it was more like 15 PSI.

Z dude

whats the PSI when driving???

92RSFivePointSlow

There's been countless posts on favorite oils and people's opinions. Since reading those posts a while back, I've done a little homework of my own. This isn't to start a flame, but it should introduce some ideas that I haven't seen many people mention on here.
I've learned that if you're using conventional oils, they're all going to break down to the first number in their viscosity rating soon after about 1000 miles anyway. The polymers break down. The farther the two numbers are apart, the more addatives are needed to hold them together. In other words, a 10w-40 will break down sooner than a 10w-30. It's been posted in here that 10w-40 is the same as 10w-30 but with more crap added to it, thats what got me interested in oils. This also means straight 30 weight is a stronger oil and will hold it's viscosity for more miles than a multi grade oil.
I use synthetic in anything I care about that I plan on going the reccomended intervals between changes. As of now this only includes my 2002 Harley Nightrain. My LO5 chevy truck with 221,000miles on it gets straight 30 weight every 3,000 miles @ $.84 a qt. My XLH chopper (for sale) gets 20w-50 @ $.84 a qt, because I find myself adding some every 500 miles.
Oil addatives- synthetic oils don't need extra garbage added to them. However, if you agree with my statement earlier about dyno oils breaking down after about 1/3 of their expected lifespan, then it may warrent adding an oil addative at this point in order to maintain oil pressure. Again, use the cheapest stuff you can find if you're keeping up with your oil changes.
Performance- forget everything mentioned above, because your engine is tight and has low miles on it, good compression, and gets very frequent oil changes. The lighter the better due to less resistance. Synthetic Amsoil is a favorite.
I'm not telling anyone you're wrong I just thought I'd kill some time pointing this stuff out so you can decide what makes your car happy.

Z dude

is there anyone here that uses AMSOIL?
if you dont mind me asking how much do you pay for ...say 10-30
10-40 whats the price you pay to what type of AMSOIL

Im curiouse as to why people say AMSOIL is soo expensive,Im thinking the person you buy from is screwing you...yes its more than WalMart oil lol

377ciTT

how much do you pick it up for?

ede

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