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The reason to say with fossil at 140K miles is because you likely have small leaks. The gunk from the fossil oil is likely to be plugging those leaks. If you switch to synthetic, it's likely to clean the gunk, which is likely to start the leaks flowing. You could try high-mileage synthetic. It's designed to plug the leaks like the gunk does. That's what it means by high-mileage.
Location: We_tside PNW (Columbia Gorge) / CO / SA TX / Thailand
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how long do you plan on keeping this car?
5,000 mile dino oil changes are fine, but I prefer 20,000 mile changes on synthetic / w 5000 mile new filter + 1 qt added.
A few of my pre 1990 cars prefer Dino oil, so if they like it better, that is what I feed them. If they show no preference, they get Synthetic, because it offers more 'margin' (higher mileage, can handle high heat MUCH better, better lubricity in case something goes wrong (oil pump / pan / cooler failure)).
Generally it won't matter, but synthetics have the edge if you have a healthy 'keeper'.
Regular oil works well enough for most cases so long as you are good at getting it changed at the required frequency.
Where regular oil doesn't work as well is on turbo charged engines. Especially smaller turbo-charged engines. Any engine like the VW TDI should be on synthetic.
So if you have a non-turbo car and are good at getting the oil changed on time then go with the cheaper conventional oil.
If you have a turbo then you should look into synthetics, if you have a small turbo engine then you should be running synthetic.
If your bad about getting your oil changed on time, then pay the extra cost and get synthetic. Small price to pay for a little extra protection during extended changes.
Quote:
Originally Posted by NC Transplants
Basically oil does not breakdown but gets dirty thus the change needed.
Basically this is incorrect. Oil most certainly oxidizes. Its one of the main reasons you have to change your oil. Its also why synthetics can go longer between changes because they are more stable and resist oxidation at higher temperatures than conventional oil.
Synthetic oil flows a lot quicker in cold temps vs conventional oil. That's why i use mobil 1 synthetic in my old 1997 chevy tahoe with 206,000 miles on the clock.
2001 Silverado with a Vortex 5.3 litters motor, and 190,000 miles. 5W-30 conventional oil replaced every 3,000 miles, and I just switched to Mobil 1 Synthetic 5W-30, not because synthetic oil is any better, but because at Walmart it costs $24.00 per gallon (almost a cheap as conventional oil).
I would not worry about oil leaks unless your motor already has oil leaks. New synthetic oils have the same additives to keep the seals from leaking as conventional oils do. But don't believe for a minute that synthetic oils are any better than conventional oils. All depends: Synthetic oils resist temperature extremes better than conventional oils. It means that you may be able to stretch the mileage by a couple of thousand miles if the vehicle is not under warranty. If it is under warranty and the automobile the manufacturer recommend the oil be replaced every 3,000 miles like the 2001 Silverado, it's up to you to use synthetic or not, since a conventional oil is designed to take 3,000 miles of more.
I have used conventional oils in the interior of Alaska for many years, usually 5W-30, and only now that synthetic oils are so cheap I have switched to these. I had a 1987 Civic Si with 265,000 miles, and a 1981 F-150 with about the same mileage. Both ran on conventional oil, at temperatures from -60 (somewhere in the early '90s), to perhaps +86 degrees during the summer. Gave the F-150 to a coworker of mine last year, and he drives it to work each day
I know personally (in my 02 Silverado with a 4.8 v8), that when I use full synthetic over even semi-synthetic, my engine revs smoother, and once warmed up my oil pressure stays a lot more of a solid 60 psi. When I use semi-synthetic my oil will be about 40psi when at idle, and up to 85psi if I give even medium throttle before its fully warmed up. I can notice semi-synthetic losing its quality almost about 4k miles. Full synthetic will go to at least 6k miles while still feeling like its at full quality.
If you DIY, full synthetic (oil, and a better filter) will cost about $5-$10 more than semi-synthetic, and about $10-$15 more than conventional, and last about twice as long. I drive aggressive and the extra mileage between changes along with the noticeable difference is worth it to me. I bought my truck with 90K miles on it 4 years ago, and it has 220K miles on it now, all from personal driving. I plan on driving this truck with this engine AS LONG AS I CAN. As long as I can do it myself, (all I really need extra is a $3 pan), its completely worth it to me. If its a car you don't care about, plan on getting rid of, and don't ever drive it aggressively, then its probably not worth the investment into longevity.
I use high mileage synthetic oil in 2 of my vehicles that are over 100K in miles. Use regular synthetic in other 2 low mileage vehicles. Always Mobil 1.
Synthetic oil is superior. If your engine is still in good condition, regardless of miles you will reap the benefits if you switch.
My silverado has in excess of 430,000 miles and I have ran Mobil 1 advanced synthetic and changed the oil and filter at 12,000 to 15,000 mile intervals since the very first oil change. It still runs perfect and smooth.
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I am using Quaker State full synthetic in my Nissan Cube right now. Normally I always run Pennzoil Platinum but after learning QS is also a SOPUS product from Shell I gave it a shot to save a few bucks. Not liking it so far, the engine in no way runs as smooth as with the Pennzoil full synthetic. The QS oil gets great reviews but I am going back to PP forever.
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