Synthetic oil
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Junior Member
Joined: Mar 2018
Posts: 80
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From: NY
Car: 1987 Firebird
Engine: 2.8L V6
Transmission: 700r4
Synthetic oil
Ive been askin around and I’ve been told that with the old seals on motors that detergents in synthetic oils make them leak. So what synthetic oil has low or no detergents and is still good??
Senior Member
Joined: Jan 2019
Posts: 576
Likes: 507
Car: 1989 Firebird GTA
Engine: Motown Aluminum 427
Transmission: TH400/GVO
Axle/Gears: Dana 44 IRS 3.75:1
Re: Synthetic oil
I wouldn't bet that was your only problem, but, most oil manufacturers are making synthetic blends for high mileage applications. Straight synthetic is slippery stuff and if there's wear, it will find and "slip" by those worn areas....
Joined: Aug 2009
Posts: 1,972
Likes: 127
From: Los Angeles
Car: 1989 IROC Convertible
Engine: 350 TPI L98
Transmission: WC T5
Axle/Gears: 3.42
Re: Synthetic oil
My entire stock LB9 and TH700R is on Mobil 1. Been on it for nearly two years. No leaks. But yes, I've had that happen. Two Volvo 850 Turbos. Put synthetic in an both started leaking.
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Joined: Mar 2016
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From: New England
Car: 1988 IROC Z Convertible
Engine: 305 TPI (LB9)
Transmission: 700 R4
Axle/Gears: G80 GU2
Re: Synthetic oil
I just stuck with conventional Valvoline. 30k mile bone stock motor..
When I switched to Mobil 1 in my 87 with about 40k Miles it started weeping.. Nothing urgent or noticeable on the dipstick, but there were little half dollar spots on the garage floor.
I only drive around 800 miles/year on the 88 so the oil doesn’t even really get dirty..
I use a really good WIX filter though.. I was always told the filter is the first thing to break down. Having 10,000 mile synthetic oil is great, but the low end filters can’t keep up.
When I switched to Mobil 1 in my 87 with about 40k Miles it started weeping.. Nothing urgent or noticeable on the dipstick, but there were little half dollar spots on the garage floor.
I only drive around 800 miles/year on the 88 so the oil doesn’t even really get dirty..
I use a really good WIX filter though.. I was always told the filter is the first thing to break down. Having 10,000 mile synthetic oil is great, but the low end filters can’t keep up.
Joined: Mar 2017
Posts: 4,255
Likes: 427
From: Portland, OR
Car: 86 Imponte Ruiner 450GT, 91 Formula
Engine: 350 Vortec, FIRST TPI, 325 RWHP
Transmission: 700R4 3000 stall.
Axle/Gears: 9 Bolt Torsen 3.70
Re: Synthetic oil
If it leaks - fix it. Full synthetic is worth it. Specifically Amsoil full synthetic. Anything less is just a compromise.
Amsoil oil filters are rated for 15,000 miles.
GD
Amsoil oil filters are rated for 15,000 miles.
GD
Joined: Apr 2017
Posts: 1,149
Likes: 445
From: Northern NY
Car: 1988 Trans Am GTA and 1979 Trans Am
Engine: 5.7 L98
Transmission: 700R4
Axle/Gears: Borg Warner 9 bolt 3.27
Re: Synthetic oil
I’ve been running Mobil 1 regular and now High mileage 5w-30 for 2 years on my l98 GTA with 81,000 miles and no issues with leaks.
Joined: Aug 2009
Posts: 1,972
Likes: 127
From: Los Angeles
Car: 1989 IROC Convertible
Engine: 350 TPI L98
Transmission: WC T5
Axle/Gears: 3.42
Re: Synthetic oil
Full synth is far, far better than dinosaur reduction. Amsoil is probably the best out there but also very expensive ($12/quart?). Mobil 1 is awesome and can be snagged at Costco or Walmart, sometimes for as little as $5.50 quart.
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Joined: Mar 2017
Posts: 4,255
Likes: 427
From: Portland, OR
Car: 86 Imponte Ruiner 450GT, 91 Formula
Engine: 350 Vortec, FIRST TPI, 325 RWHP
Transmission: 700R4 3000 stall.
Axle/Gears: 9 Bolt Torsen 3.70
Re: Synthetic oil
Actually Amsoil has an OE 10w30 that's only $7.75 retail.
GD
GD
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Joined: Mar 2016
Posts: 2,406
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From: New England
Car: 1988 IROC Z Convertible
Engine: 305 TPI (LB9)
Transmission: 700 R4
Axle/Gears: G80 GU2
Re: Synthetic oil
Good to know the Amsoil filters are rated so well..
All small block Chevys will leak eventually.. as my BMW and Porsche friends always remind me..
Senior Member
Joined: Jan 2019
Posts: 576
Likes: 507
Car: 1989 Firebird GTA
Engine: Motown Aluminum 427
Transmission: TH400/GVO
Axle/Gears: Dana 44 IRS 3.75:1
Re: Synthetic oil
that's why u gotta own one of each, that way you can show them that - eventually - they will ALL leak...
Senior Member
Joined: Jan 2019
Posts: 576
Likes: 507
Car: 1989 Firebird GTA
Engine: Motown Aluminum 427
Transmission: TH400/GVO
Axle/Gears: Dana 44 IRS 3.75:1
Re: Synthetic oil
Although there are applications for conventional oils, and rationales for using them, synthetic generally has the numbers behind it. The "cliché" that synthetic doesn't break down is really irrelevant bc it gets mixed with the byproducts of combustion just like conventional oil, things like fuel etc. will never be dealt with by a filter, and so depending on your usage, it doesn't necessarily have a big advantage in terms of longevity.
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