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Discussion Starter · #1 ·
i read a whikle back that seals intitally run on petroleum oil would start to leak if one switched over to 100% synthetic

i have to add about 1 quart of oil between oil changes..
whould i consider adding 1 quart of petroleum based oil ?

will this have any deleterious result?
will it tend to prevent the oil seal leakage induced by the change to synthetic i have read about?

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Rich Baratta
Cocoa Beach, Fla
Team Chevelle #380
May 2001 Feature Car
BSE WannaBe
[email protected]
www.chevelles.com/showroom/70_SS_454.jpg
 

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Well i cant speak for an old chevy engine but i went from petroleum castrol 10/30 in my dodge ram to mobil one full sythetic, not one drip (knock on wood) and this is with a 90,000 mile engine. I would take the plunge

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Thomas (AKA Hot66ss)
66 Super Sport Now striped frame off Project
67 Malibu Getting there.
69 El camino Beater FOR SALE Mild 355, M20 4 speed (Daily Driver)
Video of me in the Elco smoking the tires
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Rich,

I am not an expert here but I run synthetic in my Z/28 and would not add petroleum based oil for any low points between oil changes. I think this will have a negative effect on the oil properties. I hope there are better experts on this board that will pipe in.

I will add that when I chenged from petroleum based oil to synthetic, I had a leak in my rear main. I am not sure if the leak was there before as I bought the car in October and put it straight into winter storage and changed in the spring. I was using Valvoline Syntec but changed last year to Mobil 1 and the leak appears to have either reduced or disappeared completely. I put a large piece of clean cardboard under the car last year to protect my garage floor (discarded the old carboard oil soaked pieces)and either the oil is not there or the board does not show with such clean synthetic oil. I only drove the car about 400 miles last year. I am thinking the leak has stopped with Mobil 1

Back to original question. I would not add anything but synthetic between oil changes... and only the same brand.

Mytmouse

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67 SS396 350HP 4 sp 3:55 Posi Butternut Yellow w/Black Vinyl
68 RS Z/28 302 350+Hp? 4sp 4:10 Posi, Euro Red on Black
70 SS396 350HP 4 sp 3:55 Posi, Black on Black

Mytmouse A.K.A. Robert Stacho
ACES Member # 04359
 

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Rich,

I have a '90 Chevy truck with 164,000 miles on it. I bought it with 90,000 miles and I imdeiatly switched it to synthetic oil because I got it for free throught a sponsorship. I ran the synthetic for 2 years and then stitched back to cheap oil and I have never had an oil drip yet. I don't know much about synthetics but in my experience it has not shown and leak potential. Good Luck.

R.J.
 

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Rich,

After reading responses from others, I had to re-read your post. Are you already running Synthetic and asking whether adding Petroleum based product (austensibly to reduce seal seepage) to a crankcase that is 1 quart low of synthetic is deleterious to the crankcase oil? If so, I think the answer is "yes". Or are you just asking whether switching to synthetic on a used engine is deleterious...then I think the answer is "no"

Mytmouse

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67 SS396 350HP 4 sp 3:55 Posi Butternut Yellow w/Black Vinyl
68 RS Z/28 302 350+Hp? 4sp 4:10 Posi, Euro Red on Black
70 SS396 350HP 4 sp 3:55 Posi, Black on Black

Mytmouse A.K.A. Robert Stacho
ACES Member # 04359
 

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Why don't you log on to mobil.com and ask them?

Would they neglect to include a warning on the container about mixing their synthetic oil with regular oil? Not if some lawyer could prove in court that doing so had damaged his client's engine.

Can synthetic oil be mixed with regular oil? How do they produce the "synthetic blends"
that are sold by just about all major oil companies?

My $0.02
 

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Personally I run a synthetic blend that way I don't have to worry about switching back to conventional oil. As far as adding conventional oil to synthetic, DON'T do it. Synthetic oil and conventional oil cannot make a bond to properly work together. It's not a good idea. I'm not sure how they make the synthetic blend, but I know for sure you can't blend it yourself, it just won't bond together.

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68 chevelle malibu - bone stock

68 2dr - tubs, slicks, and a roll cage (race car in the making)
 

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Forget about trying to get a reply from Mobil. I don't think they know how to use a Computer yet. They just don't answer. So I said **** on it.

I did use Mobil-1 in my '87 G/N and because the turbo uses the same oil, it didn't stay clean as long as I thought it would. It's my daily driver, so I switched back to conventional oil because I had to change it after 4000km and the cost was too high for dumping it at that interval. No gain here.

My Z, I also tried it.Sure it's got less drag than conventional oil (more HP)for your engine but if your hammering throught the gears, I notice it uses more oil than conventional oil. So I switched back to normal oil too.

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Mark
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Discussion Starter · #9 ·
hey robert & other guys...let me clarify:

i changed to mobil 1 at my last oil change..
i was on the road at 3000 miles and i couldnt get in for a change so i added 1 quart of kendal since thats all i had and i needed to drive a long distance

at first i shuttered at the thought of adding petroleum based to the synthetic..but then i remembered a post that said something to the effect that seals swell with petroleum based oils but not with synthetic..once one switches from petroleum based to synthetics the "swelling" gradually disappears which then results in a leak..
so i thought that maybe it was a good idea to add some petroleum based oil whenever the synthetic is low to keep the seals snug..

i am not saying that i intend to run further than 3000 miles because i have synthetic in..i just had no choice this time around and hence added the petroleum based because i had to drive 160 miles and i didnt want to do it 1 quart low

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Rich Baratta
Cocoa Beach, Fla
Team Chevelle #380
May 2001 Feature Car
BSE WannaBe
[email protected]
www.chevelles.com/showroom/70_SS_454.jpg
 

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if you want the best synthetic oil-redline is the one.It cost more-but-outperforms the rest.they manufacture trans fluids-gear oils-and all the basic types of oil wts.
many people have heard horror stories about synthetics when they first came out and they were a nightmare. mobil 1 had nothing but leaking seals-etc...after a few years of experiments the problems were solved.
one thing about synthetic is that you do not drive it for years and then change the oil. new car guide lines have indicated 7500 mile oil changes-and-of course-the customer gets blamed for the oil failures. 3 and 3 is the best time frame as with conventional oils. Synthetic is far superior to convential oils-and after spending many $$$ on your motor-its worth it. contact www.redlineoil.com
 

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You can top up with petroleum-based oil without detrimental effects, in fact they sell semi synthetics. I have been running synthetic in my Corolla since it hit 160,000 kms. Today it has 332,000 and doesn't burn oil at all. I had the oil pan off recently and it was remarkably clean, a characteristic of continued synthetic use. Often leaks will occur on older engines because the gaskets are shearing from so many hot / cold cycles. Often these leaks go undetected for a time with conventional oils because sludge buildup masks it. When you run synthetic it will start to clear away any sludge and expose any gasket failures that may have developed but gone undetected since the sludge prevented oil from actually reaching the failed gasket. I did develop a slight leak in the oil pan, but that was due to the fact that I live in the rust belt and the car has seen 12 years of road salt (the body is rock solid though thanks to oil spray & rustproofing since new, plus I'm a freak who waxes the car every month - it looks almost brand new still!)
My Chevelle has done a lot of sitting around over the years (just over 40,000 miles since 1967) and leaks, but after an overhaul and breaking I will certainly run synthetic in it. Synthetic is especially good for cars that sit idle for long period (winter storage) because it clings to the surfaces. I used to think that it was way overpriced, but I feel differently about it now. It is vastly superior.
 

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You can freely mix dino and synthetic oils from any manufacturers without any problems. No oil manufacturer is going to put a product on the shelf that would damage an engine if it's certified for that application.

I have used synthetic oil in my Jeep (~157,000 miles) and my Corvair for many years. When I switched to synthetic in my Elky last year (~170,000 on the odo, but who knows), it developed leaks at both oil seals. I switched to Valvoline's High Mileage Engine) oil and the drips ceased.

That said, there are more anecdotal opinions about motor oil than politics or religion. I think ANY oil works just fine if you change it when you should and don't over heat the engine.

Herb Caen once said anyone can get the facts, but it takes real style to have an opinion!


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Mike Ahlmann
'69 Elky SS-396
Sunnyvale, CA
There are no atheists at 150 MPH!
 
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