I'm not flaming anyone. Nor am I spouting drivel form a group of technophobes who embrace 30's technology as the peak. My current daily driver has a computer controled diesel injection pump. I'd put an electronic ignition on a plane in a heartbeat if it were legal and cost effective. I'd use synthetic lubricants in the crank case if I felt they offered an advantage, even if it weren't 100% cost effective. What follows is my reasoning for not using them. (By the way, I use synthetic gear oil in the axles of both 3/4 ton pickups and the trans of the manual and am considering using it in the transmission of the one that's automatic. Why? Because of their superior resistance to thermal degredation and better viscosity properties at low temperatures. I'd use it in the crankcases, at least in the winter, if I lived a little farther north.)
> In that period of time neither has experienced a single valve sticking > which had been a problem previously. I have yet to have a valve sticking problem in some 4000 hours of flying with mineral based oils and some Shell semi-synthetics (Knock wood). Most of my friends that have had problems have engines that are full of carbon inside from infrequent use, short, cold flights and infrequent oil changes. It's good that you're not having the problem now, but you shouldn't have had it before either. > Oil changes (?) have been 200 hrs along with filter change. I don't feel that contaminants are consumed as easily as oil, so I would not feel comfortable going 200 hours between oil changes. Also, a lot can happen in 200 hours. I like looking at the screen every 25 hours and seeing no metal. That makes me feel good. > These 2 engines are unbelievably clean inside, So are mine. I've also got a '78 SAAB turbo with 186,000 miles on Castrol GTX, changed every 2500 or so. It's clean as a whistle inside. > The higher time engine developed a leak of the front seal which when > changed was found to be very brittle due to age. The leak was obviously > due to loosing the sludge that was acting as a seal. This is not obvious to me. I have heard of increases in oil consumption when changing to Shell 15w50. I could believe that it "finds" leaks better. > Both engines run mainly on Mogas except for X-countries when only 100LL is > available. This is a good practice, in my mind. Regardless of oil, these engines don't need or want the extra lead, on the plugs, on the valve stems, or in the oil. > I've been using Mobil 1 in my cars since it came out, 165,000 miles on one > 115,000 on another and 130,000+ on the current. See SAAB story above. The only internal engine failure I've ever had, and I've had my share of high mileage vehicles, was one time in Vermont, when I knew I had only one shot at getting it started because of a weak battery. It was about -25F and I goosed it too much. 1200 miles later I knew that that tap-tap was not just a tappet. Ended up with a failed rod bearing. Interestingly enough, synthetic oil might have protected me from myself, but it hadn't been intoduced yet. A set of jumper cables would have saved me too. Lately my plan is to keep each vehicle for 10 years. This nets out to about 120,000. We recently sold one to a friend. They got it up to 200,000 and traded it in. > The real issue is the additional lubrication gives over regular > non-synthetics. There's no arguiing this point. The question is whether there's a real benefit. > Interesting,,,, turbines which run at a bizillion RPM and much higher > temps Turbines are oranges. Internal combustion engines are apples. Turbines use roller bearings and see temperatures and RPMs that I/C engines don't (except in turbochargers). Turbine oil is NEVER exposed to combustion byproducts. > Porsche and Corvette both recommend synthetic oil,, Wonder why? Me too. What are the oil change intervals? > Remember we are dealing with a group of people who are clutching 1930's > technology to their breasts as though noting could possibly improve over > this fine technology. You're probably referring to me, but that's not the case. > allowed myself to let personal experience overcome myth and propaganda. Me too. > So unless you have personal experience please don't bombard me with urban > legends of problems due to synthetics. OK. I was born with a ratchet in my hand, at least that what my dad told me. I've been tinkering with cars, trucks, and lately airplanes since Elvis was only a prince. Here's one urban legend I'll share. In the 70's I was involved with SAABS. Mobile ! had just hit the streets. A number of SAAB turbo owners fell for the pitch and put it in their cars. The recommended change interval was 25,000 miles, if I remember correctly. Well, there was nothing wrong with the oil, but it could not hold up for 25K in the air (oil) cooled turbo bearings. The blowers got all coked up and the seals started leaking. Those cars would put down a smoke screen when hot that a Navy destroyer'd be proud of. If they'd changed the oil at 3000 miles, everything would probably have been fine. (See SAAB story above). So, MY bottom line: Even though synthetics retain their lubrication properties better than mineral oils, and even though they hold up better under extreme heat, I am not comfortable with extended oil change intervals. And I feel it's better to control the heat than use an oil that can put up with it. My C-90 never sees oil temps higher that 190 F(Calibrated gauge). When I tore it down at 1800 hours, it was clean inside. It lasted 1800 hours and 35 years. Somehow I can't see the benefit of "better" oil, no matter how good it looks on paper. So I'll keep changing the oil every 25 hours, or twice a year, or 300 miles, or whatever. I'll use a good quality reasonably priced oil. And hopefully I'll continue to see TBO on everything. Your mileage may vary. Batteries not included. John
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