How much life left in the engine?
Thread Starter
Racer
Joined: Apr 2001
Posts: 302
Likes: 0
From: South Haven Michigan
How much life left in the engine?
I have an 89 convertible with 86k miles, completely stock L98. When I bought it 6 years ago, the oil pressure seemed lower than it should be when fully warmed up (20 psi). Fast forward to now and it drops to 9-11 psi (saw 9 psi for the first time last night) when completely warmed up and sitting a stop light. It is still around 50-55 psi when I start it up cold in the morning, same as it was when I bought it. I use Mobil 1 5w-30, which was in the car when I bought it and I continue to use. It doesn't burn any oil to speak of and runs fine. I am suspecting the bearings are wearing more, increasing the gaps, lowering the oil pressure. I haven't checked the pressure with a manual gauge, but since the cold pressure is the same as it was 6 years ago and only the hot pressure is dropping, the gauge is probably fine. I have heard the adage of 10 psi per 1000 rpm, but 9 psi at idle seems way too low.
Question: How much longer should I expect the engine to last? Is this thing about to drop to zero while driving and grenade the engine?
Question: How much longer should I expect the engine to last? Is this thing about to drop to zero while driving and grenade the engine?
Race Director
Joined: May 2001
Posts: 14,165
Likes: 9
You're fine. 86k miles is nothing for a small block chevy. You might try running a slightly thicker oil, say 10w30 and see if it makes any difference. In theory it shouldn't make a difference when fully warmed up, but in practice it always seems to make a little difference.
Le Mans Master
Joined: Oct 2003
Posts: 6,130
Likes: 2
From: seattle WA
I think I would hook up a mechanical guage to see if there's a malfunction with your guage.The oil pressure you're talking about may be acceptable-but I think it's not right unless at some point something happened to the engine.Could be the sending unit.
Advanced
Joined: Feb 2005
Posts: 90
Likes: 0
From: Bolivar TN
I've been wondering if my guage is right... At cold start it always shows 80. Driving 65 mph, it shows 70-80. The lowest I've seen was 55, that was sitting at a red light in Memphis traffic about 90 degrees outside temp.
Oh yeah...86 model, 115,000 miles.
Oh yeah...86 model, 115,000 miles.
Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,063
From: altered state
St. Jude Donor '05
Dont feel bad..Even cold, my pressure is never more than 50 punds or so. That's with a thicker oil. At idle its around 15-20 which is fine. When its hot, it drops down low like yours. Remember, these cars idle very low so your pressure may be also. I wouldn't worry about it. 124k miles here, never smokes. Small block Chevys usually only require 10psi per 1000 rpm. Heck my last motor (fresh) only idled at 15 psi with a Malling hv55 pump. Machinist said 
Team Owner
Joined: Dec 2000
Posts: 21,094
Likes: 282
From: Phila., PA burbs
Just keep up with the routine maintenance and you'll be fine. I keep expecting something to let go on my L98 and it just keeps getting stronger, even at 116k....................and I beat the hell out of it 
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Melting Slicks
Joined: Jul 2004
Posts: 2,018
Likes: 1
From: OR
Originally Posted by rick lambert
I think I would hook up a mechanical guage to see if there's a malfunction with your guage.The oil pressure you're talking about may be acceptable-but I think it's not right unless at some point something happened to the engine.Could be the sending unit.
First, look up the spec for what's normal. Then check with a mechanical gauge.
With low pressure at idle and no other problems noted, smoke, knocking, ect, the next thing to check would be the pickup tube for the oil pump and the oil pump. If you haven't owned the car since new, you don't know for sure how it was treated. Seen a lot of cars where sludge choked off the pickup tube screen due to infrequent oil changes and the engine never getting up to operating temp. There aren't enough miles on that car for the bearings to be shot. jmo
Team Owner
Joined: Sep 2001
Posts: 62,160
Likes: 1,733
From: Athens AL
C7 of the Year - Unmodified Finalist 2021
C4 of Year Finalist (performance mods) 2019
I'm suspecting you either have a bad sender or worn pump. The sending unit is a cheap fix and you need to remove the distributor (and/or the wiper motor) as its screwed into the back of the intake manifold. Its connector also goes bad too, so you may have to cut & splice a new one on.
Otherwise change the pump, Melling M-55A is what I use.
Otherwise change the pump, Melling M-55A is what I use.
Team Owner
Joined: Sep 2001
Posts: 62,160
Likes: 1,733
From: Athens AL
C7 of the Year - Unmodified Finalist 2021
C4 of Year Finalist (performance mods) 2019
Originally Posted by cyclebuyer
I've been wondering if my guage is right... At cold start it always shows 80. Driving 65 mph, it shows 70-80. The lowest I've seen was 55, that was sitting at a red light in Memphis traffic about 90 degrees outside temp.
Oh yeah...86 model, 115,000 miles.
Oh yeah...86 model, 115,000 miles.
Advanced
Joined: Jun 2004
Posts: 83
Likes: 0
From: NC
1990 Coupe All Original - 54500 miles
Lucas makes an oil additive that they state raises oil pressure. It is a full synthetic and on the bottle it says that it does not void any warranties so I gave it a shot on my last oil change. My oil pressure use to be around 40 or so, and now since the additive went in I run around 60 or so. They suggest you substitute this additive for one quart of oil at change. It is somewhat thick which always worries me but so far engine seems to be happy, (always want the best for the "All American Muscle Machine").
Matt
Lucas makes an oil additive that they state raises oil pressure. It is a full synthetic and on the bottle it says that it does not void any warranties so I gave it a shot on my last oil change. My oil pressure use to be around 40 or so, and now since the additive went in I run around 60 or so. They suggest you substitute this additive for one quart of oil at change. It is somewhat thick which always worries me but so far engine seems to be happy, (always want the best for the "All American Muscle Machine").
Matt
Thread Starter
Racer
Joined: Apr 2001
Posts: 302
Likes: 0
From: South Haven Michigan
I added the synthetic version of Lucas Oil Stabilizer and it did raise it at idle from 9-11 to 14-16 lbs (fully warmed up, in drive, stuck at a traffic light, oil temp @230 degrees). It is higher across the board as well. The service manual says the minimum oil pressure is 6 psi @ 1000 rpm. It is in the 20's at 1000 rpm so I am probably worrying about nothing.
Race Director
Joined: Mar 1999
Posts: 16,950
Likes: 0
From: Stafford, Virginia Kittah, Kittah, Kittah...
Originally Posted by bogus
I would start with the sending unit, too.
GM gauges are notorously inaccurate...
GM gauges are notorously inaccurate...
The car had 136K miles on it when I sold it and I ran a carfax on it a few years back just to see what became of the car... The carfax showed it failed it's first smog check at 18xK miles...
I miss that old car... Probably the most reliable car I've ever owned...
