Contour Enthusiasts Group Archives Forums Modifications Duratec Maintenance switching to synthetic oil...

ive heard that switching can cause leaks on older, high milage cars. my car had been running regular oil, and i wanna switch to synthetic. its a 97, and has 73k miles on it. think its safe to switch? also, i heard something about flushing out the engine, and also whats the best oil to use?

I highly doubt that simply switching to a synthetic oil would cause you car to start to leak. Only if you put a thinner oil in would I believe that it could happen. But don't take my word on it! I haven't been around for too long yet!

I've heard that certain synthetics do not have the detergent (keeps the engine crud in solution) properties of good ol' natural oil, and so tend to leave deposits of engine crud in your oilpan. Ideally, you want an oil that doesn't allow the crud to settle-- this way you can get rid of it when you change your oil.

As for which brand to use? I use Pennzoil Full Synthetic, but only because I used regular Pennzoil for years in my Taurus Wagon. I've read good things abour Pennzoil.

Originally posted by PoopStainz:

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ive heard that switching can cause leaks on older, high milage cars. my car had been running regular oil, and i wanna switch to synthetic. its a 97, and has 73k miles on it. think its safe to switch? also, i heard something about flushing out the engine, and also whats the best oil to use?

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Last things first. The best synthetic oil is likely Mobil-1 although Red Line is also quite good it is harder to get.

I've run Mobil-1 in my modified Merkur XR4Ti's since 1987 (they run much hotter than the 2.5L - the cooling system can't keep up with the turbo heat for long blasts at 18psi at 21psi I could actually see the temp gauge increase!!!!)

If your motor is in good shape everything should be fine. I bought my 98 Mystique in March with approx. 68,000 miles on it and swithced to Mobil-1 to go to BMW's Advanced Driving school in June. I ran the car HARD (consistantly passing 6-7 BMW 325's during the afternoon fast lapping sessions on the 1.6 mile road course ) without any trouble.

Everyone else would come in and open their hoods, etc., between the 20 minute sessions while I just parked and relaxed. I was the only Ford there, except for my friends perefectly built AC Cobra replica (stroked 351W with 4 2 barrel chromed Webbers, etc., etc.). There were 50 drivers in 3 different groupings and most of them wanted to know what the hell I was driving and how it was so fast.
My reply was that it was just a little 4 door family sedan made by Ford running on all-season radials (205/55/15 Toyo FZ4's w/5% tread left). The only modification was SVT front rotors and theirs a Ford sticker under the hood (which no one got to see) that indicates the PCM was modified by Ford back when it was and undercover police car. I loved every minute of it.

I've since installed a KKM from CTA and my mechanic is just installing a rear SVT motor mount, front insert, 19mm rear bar w/ Performance Ford's end links, KVR pads w/ braided lines, new brake fluid, urethane bushings, and an oil change in readiness for Saturday and Sunday's run on the road course. Can't wait

Regards, Alan Coles

It's not the oil. Sometimes switching to synth will cause leaks because the seals are shot. The synth oil can remove deposits, some of which are prevnting leaks. In prctice this doesn't happen, but it can. I switched my Mustang from dino juce to Mobile-1 at about 65K. 20K later no new leakes. Do the switch, you won't regret it.

Also, in the early 70's there was an actual problem with seals that were designed to absorb a bit of something from the oil, which caused them to remain at their specified thickness. The early synth oils did not have this stuff, and consequently, the seals shrank and would start leaking. This problem was quickly remedied by adding whatever-it-was to the synth oil. Problem solved by 1975, but the myth lives on almost 30 years later.

I switched to Mobil 1 at about 50k on my 96 with no problems or regrets.