Converting 1995 Chevy C/K over to Synthetic?

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I bought a 1995 Chevy Truck that has 56,000 miles on it. The odometer is 6 digits so it’s not as if it has rolled over.

The truck has had 2 owners, the person I bought it from owned it for the last 22 years. He only used Conventional oil in it.

Has anyone had any success with changing an older vehicle over to Full Synthetic and not had it leak oil terribly after making the change?

When I was a teenager I had a Ford Escort and accidentally put synthetic in it not realizing the small detail on the oil bottle and it started leaking like a sieve and I had to replace a seal on the front of it. This truck leaks very very little currently but I’ve heard Synthetic will clean out an old car’s buildup and possibly cause leaks?

The manual says use 5W-30 due to living in a colder climate (WI). The truck will probably put on no more than 3,000 miles per year so it sits a lot and I'd like to extend the oil change intervals out as long as possible.

Thanks,
Fordguy88
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Had a 1995 Chevrolet Tahoe 4x4 K1500 5.7L. Switched to synthetic at 160k miles, previous owners (before 150k) used Jiffy lube specials, I'm guessing the cheapest conventional. In my case High Mileage synthetic 10w30 actually slowed some existing leaks down. Switched to Mobil1 0w40 later on and used that until sold the Tahoe at 180k. My OCIs were 3k-4k miles.
 

fordguy88

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Had a 1995 Chevrolet Tahoe 4x4 K1500 5.7L. Switched to synthetic at 160k miles, previous owners (before 150k) used Jiffy lube specials, I'm guessing the cheapest conventional. In my case High Mileage synthetic 10w30 actually slowed some existing leaks down. Switched to Mobil1 0w40 later on and used that until sold the Tahoe at 180k. My OCIs were 3k-4k miles.
What was the factory recommended oil to use?

It's interesting to see some people use different oils at different intervals of a vehicles life. I've always just stuck to the book and changed over to high mileage as needed.
 

LDM

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Had a 95 Tahoe with 240K miles on it before the head gasket blew. I used whatever oil was on sale and it never leaked oil once. Last 10 years of its life was mostly semi syn and full syn oil. 5W30 was all I ever put in it too, which is the factory recommendation on the oil cap and the manual. The old SBC design really isn't going to be picky on oil, you could probably run it on anything from 0W30 to 20W50 and won't see any difference. Especially a stock TBI 305 or 350 from 95.
 

fordguy88

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Had a 95 Tahoe with 240K miles on it before the head gasket blew. I used whatever oil was on sale and it never leaked oil once. Last 10 years of its life was mostly semi syn and full syn oil. 5W30 was all I ever put in it too, which is the factory recommendation on the oil cap and the manual. The old SBC design really isn't going to be picky on oil, you could probably run it on anything from 0W30 to 20W50 and won't see any difference. Especially a stock TBI 305 or 350 from 95.
Yes, this is a 2500 5.7L V8.

I'm such a chicken when it comes to Oil. Usually only buy Mobil1. But then I look at the Walmart brand and the price and want to pull the trigger, but it almost seems too cheap to me. But on the flip side with groceries i'll buy as cheap as it gets (Aldi, etc).
 

LDM

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Yes, this is a 2500 5.7L V8.

I'm such a chicken when it comes to Oil. Usually only buy Mobil1. But then I look at the Walmart brand and the price and want to pull the trigger, but it almost seems too cheap to me. But on the flip side with groceries i'll buy as cheap as it gets (Aldi, etc).
I wouldn't worry about it. Especially the synthetic part. My 89 Camaro has the 350 TPI motor, been running synthetic in it since it bought it over 6 years ago. No leaks other than the rear end, which was due to a bad job on my part using RTV when there were no 9 bolt gaskets available anywhere. Just fixed that last week with new fluid and a real gasket.

Now my 94 Camaro, leaks are different story. But she was always leaking something. Too much modding and power I suppose. Ah well, the new 383 is being built and hopefully will go in next year. Should solve my modding and leaking problems for a while.
 
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I bought a 1995 Chevy Truck that has 56,000 miles on it. The odometer is 6 digits so it’s not as if it has rolled over.

The truck has had 2 owners, the person I bought it from owned it for the last 22 years. He only used Conventional oil in it.

Has anyone had any success with changing an older vehicle over to Full Synthetic and not had it leak oil terribly after making the change?

When I was a teenager I had a Ford Escort and accidentally put synthetic in it not realizing the small detail on the oil bottle and it started leaking like a sieve and I had to replace a seal on the front of it. This truck leaks very very little currently but I’ve heard Synthetic will clean out an old car’s buildup and possibly cause leaks?

The manual says use 5W-30 due to living in a colder climate (WI). The truck will probably put on no more than 3,000 miles per year so it sits a lot and I'd like to extend the oil change intervals out as long as possible.

Thanks,
Fordguy88
Top
Back in the day, some synthetics had high Ester content which swelled seals, sometimes so much that they would leak. It should not be a problem today. my method has always been to install first with cheap filter, synthetic cleans better than Dino and you could get lots of grunge in the filter. Change filter only, top up with synthetic, rinse and repeat 2 more times.
 
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What was the factory recommended oil to use?

It's interesting to see some people use different oils at different intervals of a vehicles life. I've always just stuck to the book and changed over to high mileage as needed.
Straight from the manual:
"SAE 5W-30 is best for your vehicle. However, you can use SAE 10W-30 if it's going to be 0°F (- 1 SOC) or above. These numbers on an oil container show its viscosity, or thickness. Do not use other viscosity oils, such as SAE 20W-50."
I did not use 5W30, because after a highway run the oil pressure always dropped low enough to cause the oil pressure light to come on. 10W30 didn't have that issue, neither did 0W40. Mobil 1 0W40 did give me the least amount of valvetrain noise. And yes, I did violate the owners manual and used Supertech 20W50 and Mobil1 15W50 in it a couple times in hot & humid NC summer.
 
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Back in the day, some synthetics had high Ester content which swelled seals, sometimes so much that they would leak. It should not be a problem today. my method has always been to install first with cheap filter, synthetic cleans better than Dino and you could get lots of grunge in the filter. Change filter only, top up with synthetic, rinse and repeat 2 more times.
I thought that esters swelling seals helped to stop or prevent leaks, isn't that what's in many of the "stop leak" products? Wasn't the problem of leaks generally attributed to the PAO cleaning out crud that had plugged a potential leak? And didn't they solve that problem by adding additional "seal swellers" to synthetic oil?
 
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What specification does the "synthetic" meet that the "conventional" does not ?
Actually the lines are blurred, The truck has been run on "semi-synthetic" for years.

I would run "conventional" 5W30 which is actually semi synthetic and change oil and filter once a year.

Now about that transmission fluid and rear gear lube ?!
 
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I switched to synthetic in a similarly-engined vehicle with no problems, in fact the rear seal leak actually slowed down. It was a 1993 Chevy Caprice with the 305 and about 120k on it. I switched to Mobil 1 10w30 high mileage.
 
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I run everything (except the Piper) in my sig and our DD's on synthetic; Mobil1 and redline. I have experienced increased leaking when switching from conventional to syn on my older British cars and know many others who have also experienced that but 1) that was years ago and 2) the vehicles I play with leak anyway so a few more drips or larger puddle is an acceptable tradeoff.

You will be fine, but I would run a short interval for the first cycle.
 
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I always like to bring up the fact that for the last few years most conventional oil have been blends anyway, especially if you have been using 5w30.

Valvoline Advanced or their blend is what I would use and at 3k would do annual changes in the spring.
 
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I thought that esters swelling seals helped to stop or prevent leaks, isn't that what's in many of the "stop leak" products? Wasn't the problem of leaks generally attributed to the PAO cleaning out crud that had plugged a potential leak? And didn't they solve that problem by adding additional "seal swellers" to synthetic oil?
you are correct And the old swollen seals would sometimes just fall apart. Spot on with PAO cleaning out crud the only thing stopping leaks, Rear mains never seemed to be an issue, but there are many seals on the front and nothing is magic, a swollen old seal will drag more on the rotating component and sometimes fail.
 
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I would go to Costco and buy a box of their Kirkland 5w30. Or online. Your 350 Chevy will love it.
I would service it once a year and swap the filter every other service.
This is what I do with our trusty Tundra.

Enjoy your new truck.
 
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