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Old 10-10-2000, 10:45 PM   #1
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Question Synth oil in a turbo RS, to use or not?

I WANT YOUR OPINION OF WHETHER TO STAY AWAY FROM SYNTHETIC OIL WITH A TURBO AND OPEN DECK.

I was talking with JC Sports the other day, and was told to not use my AMSOIL 5W-30 synthetic oil for a few reasons.

One: With boosted cars using a horizntally opposed flat 4, the head gaskets are more likely to leak/seep. True, or false? This is ALSO what the local dealership's current turbo guru says (the owner with an over 20 psi 2.0L turbo), and he recommends Valvoline turbo formulated dinosaur oil. I also asked my friend Dan at Spectrum Motorsports and he independantly recommended valvoline turbo formulated dinosaur oil. So, maybe they are onto something, since they can't all be wrong?

I once read at alt.autos.subaru that if you change to synthetic in a car with high mileage, that you are more likely to experience seeping than if you start early. I went to synthetic oil in my RS at 10,000 miles when I had my last oil change, with no problems in 1,500 miles, but I am not under boost yet. My personal experience with changing to synthetic oil was in my '93 Taurus SHO I changed at 78,000 miles to synth, and in the next 20,000 miles went through two rear main seals from the leaking.

Two: They all recommend that the oil to be changed more often in a turbo RS than most of us can afford if we are using $5.70/qt 25,000 mile synth oil. So they don't agree with extended drain intervals with a turbo. I had always planned to change the oil every 7,500 miles/6 months with the synthetic oil, since the filters are only good for that long, and Subaru might not like me ignoring their minimun 7,500 mile oil change intervals. (they'll like the turbo less)...

So, without saying that all three sources above are full of it, knowing they did all agree independently - what do you guys recommend?

Larry "opened up a can of worms" Ganz www.ImprezaRS.com

PS: I am an AMSOIL dealer and would like to continue using their products, but will not tolerate oil leaks and other problems from choosing the wrong oil for this application.
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Old 10-10-2000, 11:04 PM   #2
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I've never heard of this problem, and I'd imagine 10w40 or15w50 synthetic would be the best possible protection, turbo or not. With the lower stress of an NA application (like mine) 5w30 is a good compromise, but with gobs of power on tap, I'd want the best possible.
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Old 10-10-2000, 11:06 PM   #3
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From what i remember of a thread a while ago on www.scoobynet.co.uk people recomend that you use non synthetic oil on a new engine for the first 5 or 10,000 miles not sure which as it helps the rings or something to bed in.

Anyway goto the Scoobynet site and do a search under Oil or even Mobill 1 or Mobill 1 Motorsport etc
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Old 10-11-2000, 03:38 AM   #4
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I've been running Mobil 1 5W-30 in my RS since the 1500 mile mark. I turbocharged my RS right around the 6000 mile mark. I am now up to 28K miles. I change the oil every 3 to 3.5K miles. The passenger side valve cover has experienced a little seepage, the driver side is dry.

IMO, there is no reason NOT to run synthetic in a turbocharged RS. More over, most of the turbocharged RS's use the engine oil to not only lubricate the turbo, but also to COOL it. There is a huge amount of heat generated in the turbo. The heat will hasten coking in conventional oil.

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Old 10-11-2000, 03:47 AM   #5
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Hey Larry, I can't help you with your question, but I did want to point out that somewhere in all your dealer stuff there's a single sheet of paper with recommended drain intervals on it. It's not too impressive looking, so it may be hard to find (I think the print is blue). Anyway, I know that Amsoil does recommend a shorter drain interval if your car is turbocharged. I don't have the sheet right in front of me, but your thoughts on drain intervals sounded about right for your turbo.

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Old 10-11-2000, 05:45 AM   #6
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All t-charged engines experience higher internal pressures than N/A engines do. So it follows that all of these have a higher chance of seeping/leaking with any type of oil and, since synthetic oil is more slippery than conventional oil it will probably leak more....but it won't cause a leak if there isn't one there already.

I use Amsoil exclusively on my cars and I have a 1984 T-charged Volvo with 184,000+ miles on it and the original turbo.

I think I'm doing the right thing.

Phil
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Old 10-11-2000, 06:41 AM   #7
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Here's the kicker....if you ask this same questions to RX-7 turbo guys, they all swear up and down to stick with dino oil instead of synthetics.
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Old 10-11-2000, 08:04 AM   #8
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Gambit--That is because ALL rotaries burn about a quart of oil every 1500 miles and it needs something that burns cleaner and more efficiently, therefore, they use non-synthetic oil.
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Old 10-11-2000, 10:38 AM   #9
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I think the life expectancy of the average turbo (turbo itself) is around 70,000 miles?? A friend of mine and I had nearly identical turbo Eclipses. He used dino oil...his turbo blew at 61K. I used syn and mine was still going strong when i got rid of it at 174K. Now i know the oil is not the only factor in that, but I am conviced it was at least ONE of the factors.
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Old 10-11-2000, 10:45 AM   #10
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OS: Is it bad to switch back and forth between Synthetic and Regular motor oil?
(using redline before track days/months for up to 5,000 miles, and Castrol GTX for daily driving months up to 3,000 miles)
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Old 10-11-2000, 10:49 AM   #11
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A turbo should last longer than 70k miles. The water cooled turbos that we are using should go well past 100k miles between rebuilds if treated with care (regular oil changes, letting it cool after hard runs).
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Old 10-11-2000, 04:22 PM   #12
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FWIW, I think most turbo'd RS's are NOT using water-cooled turbochargers.
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Old 10-11-2000, 05:18 PM   #13
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Stick with synthetic.

Trust me on this, I started putting synthetic in my old subaru turbo after many years of the previous owner using POS normal oil. The oil would be black after 250 miles becasue of all the carbon comming off of the inside of the motor. Also found a 1/4" gap in the pass side valve cover gasket that had been compleately plugged with carbon.

On the SHO, I would say that the rear main seal #1 just went bad, and would have leaked oil anyway, and #2 was defective or installed wrong. On my cars running synthetic not one ever leaked oil from any of the shaft seals (cam, crank, etc.)
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Old 10-11-2000, 05:43 PM   #14
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synthetic oil is the best,if you drive hard and can afford it...then use it,ive used it for 15years from 1000mi. and on ,never a problem....NEVER!

my rs is turbo charged and has 15k on it.synthetic in it since 1000mi.
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Old 10-11-2000, 07:06 PM   #15
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Hi guys!!
I'm using MOTUL 10W-40 on my 2.5RSt. I use it every day (10psi) and no problems whatsoever....
It has a Garrett T28 Ballistic (water cooled). Remember the water on water cooled turbos is not really for cooling purposes, even though it helps a lot, it's for ANTI FREEZE. If you live in Canada, or any other freezin'place, remember that metals "shrink". If the turbo's inner shaft "shrinks", over time, start after start it will be destroyed due to the gap between it & bearings....

just my 2.5 cents......
PEACE!!!
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Old 10-11-2000, 10:19 PM   #16
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Larry,

I'm surprised that your surprised that an engine seal on a Ford leaked??

Every Ford product that I have owned (trucks especially) have had leaking rear engine seals within 12 months after purchase. Even the guys at the Ford dealership used to laugh and say "Hey, its a Ford! Its supposed to have a leaking rear seal". Its like a certificate of authenticity with them or something (ya I know the motor was Yamaha design but Ford did have some input...probably the engine seals). But I digress.

I completely agree with those that say synthetic should be used. SteveS already mentioned the primary reasoning that I would use a synthetic on a turbo'd car, but in general, MOST of the wear that you create in your car is during cold start-up. It's been conclusively proven that synthetics are far superior to dino oils in this respect.

My 2 cents.

Cheers,
MB
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Old 10-12-2000, 01:24 PM   #17
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So, the general concensus is that I should use the synthetic oil I bought?

I bought the AMSOIL 25,000 mile oil and the Super Duty 7,500 mile filter, and was planning to do the changes every 7,500 miles (maybe with an oil analysis at 3,750 miles). It was $35, and doing it myself will eliminate labor charges and only cost me $70 a year. I have a Fumotovalve already, so I won't need crush washers for the drain plug.

But, having to replace leaking head gaskets is beyond my skills wishes or desires... I'd love more feedback please! I only have two more days to decide what to do.

Larry www.ImprezaRS.com
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Old 10-12-2000, 01:38 PM   #18
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Larry,

I've been running synthetics for the past ten years and I really think you would be better off running the synthetic. A long time ago Subaru told me that the synthetics were not recommended because of seepage problems. Some of the older Subaru 1.8 OHC engines were prone to seepage and it was worse with synthetics. I spoke with an engineer at Mobil and he said the new generation synthetics have additives that address the problem.

In my 85 Subby RX Turbo I ran synthetic with no problems. The turbo lasted 130k. As far as the Fords, I totally disagree. I ran Mobil 1 exclusively in a 96 F-150 302 V-8 and a rebuilt high performance 400M in my car with absolutely no seepage (73k on the 302 and 110k on the 400M). I also ran Mobil 1 in my GM 4.3 High Output marine engine in my boat. Never, ever a problem.

If worse came to worse Larry, I would rather have the best protection for my engine and live with a little seep. Heat is a motor oils worst enemy and turbos generate a lot of it. No dino oil can compare to a good synthetic when it comes to thermal breakdown.

Just my $0.02

Punk
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Old 10-13-2000, 12:00 AM   #19
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The SHO uses a yamaha (or at least used) engine. The regular ford taurus engines had oil leaks and power steering up to about 96/97 when they pulled their heads out of their collective . . . Anyways my 1990 3.8Lv6 tuarus had to have the power steering line replaced every 2 years (twice for me), and had a cover leak (mechinc said). I knew nothing about cars excpet to change the oil between 3K and 5K. I justed wanted oil changers or whoever had.

as for oil, one of my last cars was a 93 saturn sl2. I used redline 10w30 in it (84K miles). no leaks after after 116K miles (then I totaled it). Since I have no plans to turbo my new RS for a long time, I plan to use redline or mobile1 10w30 after 3K miles. One of the reasons, I read in the jeep bible that the U.S. has a law(?) that says car manufacturers cannot use synthetics for testing mpg rating. Also the guys in the jeep bible highly recommend the synthetics for all jeeps, if you want to join the million mile club.
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Old 10-13-2000, 06:51 PM   #20
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Hey Larry- check this out.
http://members.nbci.com/minimopar/oil.html

That's a link to that Mopar guy that did the oil filter study. He also wrote up a page about motor oil, with a pretty good general overview and some personal experiences. It's worth a look.

Rich
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Old 10-13-2000, 11:30 PM   #21
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Well, here is the deal, according to JC - the concern with synth oil is not the heads or valve gaskets, it is a concern with oil blowing by through the "Legacy" turbo compressor I am using.

However, I only have to change from synth to regular oil if the synth blows out and causes white smoke in the exhaust, and with regular oil it should all return to normal.

Larry www.ImprezaRS.com
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