Has anybody switched from high mileage oil to regular synthetic?
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Some oil company reps have admitted privately that "high mileage" is the same formula as regular oil, just with a different label. The AT-205 Reseal that Uncle Scotty hawks can sometimes help slow leaking front and rear main oil seals, but does nothing for regular gaskets like oil pans. The "full synthetic" oils on the market are just hydrocracked dinosaur oil. They're no different on seals than non-synthetic. The very few true synthetic Group V ester-based oils may make older cars leak more, but that's a rare exception. You can use Kirkland or Super Tech synthetic (same oil) and be good for your car and your budget, just don't fall for the extended OCI bullshit. Six months or 5k is the best bet for longest life.
A good friend gave me a 1998 Chevy pickup that he was using high mileage oil. I went back to regular synthetic and a few months later developed a major rear main seal leak. I also have rebuilt automatic transmissions and tearing down a unit that used additive was very obvious. The seals over time turned to loose-fitting mush. I don’t know if there’s any correlation but reading your post has really made me think about it. I will be replacing the rear main seal soon and I will inspect it for those characteristics. I’ll let you know if you want.
My cars have high miles. I don't use high miles oil unless there is an oil leak that I'm not ready to fix.
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You should never mix Conventional Oil with Hybrid Blend or Synthetic Oils. Use a high quality brand. Watch some of Scotty Kilmer YouTube videos or Car Wizard on YouTube. Most additives are not recommended. If you have a leak, fix it right. Don't overfill oil level. Revving your engine damages it, letting you car engine Idle for more than 5 minutes is bad too. Starting up your car in the Winter is bad because lack of viscosity as oil sits on bottom of the pan and becomes thick, so don't idle too long, get in and go. Some oil additives do work but most do not.
Some reasonable advice, some old wives' tales. "Never mix . ." - nonsense. "High quality brand" - meaningless. API SP and ILSAC GF-6 are the latest industry specs. The color of the bottle and the brand name mean little or nothing.
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Mostly this ^. My V6 Sienna went from whatever was being used up to 35K when I bought it, to a synth blend every 5K. At 100K I went to High Mileage synth blend, just because. At 130K I went full Kirkland synth, just to keep the garage consistent and save a few bucks; saw no leaks, felt no shudder from an already-dead-quiet engine, perceived a slight mileage bump (but I'm the guy who swears the van runs better after a wax!). With pandemic realities, I'm changing the oil every 9 months or so, way under the 5K interval, and feeling a bit guilty about it; I justify my footprint by rocking a 21-year-old van, often with 6 people in it, vs an idiotic 3-row SUV cosplaying as an off-road vehicle. Now at 160K, I'll sell because rust way before seals become an issue, and someone else can do the second timing belt and easily see her into her third decade/250K miles.
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Most of my cars came with no engine in them, so I fully re-did every seal and oil pan silicone when installing the engine, so I use normal non high mileage oil.
I know mobil1 is better but it’s just too expensive. Plus I change every 4K miles. If I had longer intervals maybe I’d go with Mobil 1
that interval was made with conventional oil in mind. Probably not a bad idea to change it every 5k miles, but it can go longer if you use the right oil.
If you use synthetic oil, Mobil1, you go 5k miles not 10k how the shop says, you will be ok.
In that case I’d just go with a cheaper synthetic oil. Why spend more money only to change it at 5k miles?
Dude it’s not going to make a difference. That’s not protecting your investment. That’s just wasting money and oil for no reason than to make yourself feel better.
If it is not going to make a difference, why is one more expensive than the other one?
Because it can actually last more than 10k miles. But if you’re changing it every 5k miles you’re just wasting money and oil. No other synthetic oil actually advertises 10k intervals. Only Mobil1 does.
In general, though, modern cars can manage 5,000 to 7,500 miles between oil changes. If your vehicle calls for a blended or full synthetic oil, you can push that to 10,000 miles. Old cars (i.e., those that date back to a time before synthetic oils became mainstream) will have relatively short oil-change intervals in comparison.
If your car doesn’t get much exercise, you may wish to consider changing the oil based on time rather than mileage. You shouldn’t keep the same oil—whether conventional or synthetic—in your car for more than a year. In fact, some experts advise that you change your car’s oil every six months, regardless of the distance driven.
The more stress you have on the engine, the sooner you’ll need to replace the oil. For instance, if you haul and tow heavy loads or drive in very hot, cold, or dusty climates, your car will likely require more frequent attention, even if the oil is synthetic. Driving short distances (say, less than 10 miles) on a regular basis could also lead to oil breakdown, as the engine (and its oil) may not have adequate time to heat up.
If your car doesn’t get much exercise, you may wish to consider changing the oil based on time rather than mileage. You shouldn’t keep the same oil—whether conventional or synthetic—in your car for more than a year. In fact, some experts advise that you change your car’s oil every six months, regardless of the distance driven.
The more stress you have on the engine, the sooner you’ll need to replace the oil. For instance, if you haul and tow heavy loads or drive in very hot, cold, or dusty climates, your car will likely require more frequent attention, even if the oil is synthetic. Driving short distances (say, less than 10 miles) on a regular basis could also lead to oil breakdown, as the engine (and its oil) may not have adequate time to heat up.
Depending on the maintenance history of the vehicle, oil change intervals could be anywhere from 3-10k.
For giggles, I’d like to see what the inside of the short block looks like on a high mileage Toyota engine. Some have become sludge messes due to neglect. It’s a different convo if it was a 1 owner.
Engine needs lube, whether it’s conventional or synthetic. The leak isn’t limited to the oil pan. The timing cover, rear main seal, front seal or valve cover gasket.
For giggles, I’d like to see what the inside of the short block looks like on a high mileage Toyota engine. Some have become sludge messes due to neglect. It’s a different convo if it was a 1 owner.
Engine needs lube, whether it’s conventional or synthetic. The leak isn’t limited to the oil pan. The timing cover, rear main seal, front seal or valve cover gasket.
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