Is it better to use synthetic motor oil on a car with 100k m or "high millage" multigrade oil?

Question

Is it better to use synthetic motor oil on a car with 100k m or "high millage" multigrade oil?

Answer 1

My husband and I use a synthetic motor oil in our cars. He has a 2 year old Cadillac and I have a 1994 Ford Explorer with almost 100,000 miles on it. We were told the synthetic oil was really good to use and so far, we have been pleased with the performance of both cars. Good luck with your choice.

Answer 2

I don't know what you have been using previously, I have found that if i use conventional, and then switch to synthetic- the engines sometimes get leaks at the front and real main seals.  A car with that high of mileage does just fine with conventional oil,  and i personally don't use "high mileage oil".  I haven't found any advantage to using it.  the best thing you can do is continue with what has been used previously and change the oil and filter every 3000 miles.  

Answer 3

Although high mileage motor oil hits you in the pocket book it's worth it. The old mechanics adage is "you can pay me now or pay me later". The more effort and care that is put into the vehicle the longer it will last. It's a give and take thing I guess. I have '95 Dode Ram with close to 200,000 miles on it and have used nothing but high mileage since 100,000. I'd rather pay the price now.

Answer 4

The only real advantages to synthetic oil are increased drain intervals, better cold weather viscosity (easier starting and better protection at start-up in cold temperatures), and better engine protection when and if your engine overheats.

Except for the last two advantages, it doesn't lubricate your engine any better than (good) conventional oil. It's more expensive, so that pretty much cancels out the "advantage" of extended drain intervals, which I don't see as much of an advantage anyway.  I like to change oil and filter every 3,000 miles anyway, just to get all that c**p out of my engine.

In my opinion, it also doesn't matter if you switch back and forth between conventional and synthetic, not that you'd want to anyway.  

If you do switch to synthetic after using conventional for a long time, be prepared to have a LOT of carbon deposits loosened up by the synthetic and deposited in your filter.  After switching, I'd replace the filter at 1,500 and 3,000 miles, then again when you change the oil at maybe 6,000 - 7,500.  Then just change the filter when you change the oil again.

Lastly, no matter what anyone says, I wouldn't run synthetic in a brand new engine.  I'd let in break in with conventional oil until the first oil change.

I don't even think you have to use a "High Mileage" oil unless you're burning more than a quart of oil between changes.

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The answerer above made an excellent point about leaks developing after switching to synthetic.  It's so good at loosening old deposits of carbon and sludge that it can remove deposits that were bridging small gaps around seals.

Answer 5

ya one more thing, be careful when you buy synthetic oil (which i recommend,( i switched my '93 f150 over at 120K miles and developed no leaks) but a lot of "synthetic" oils on the shelf are not actually synthetic. the biggest difference between the fakes and a true synthetic, are that true ones are made from natural gas, not petroleum oil (think about it how can you take oil, turn it into oil and call it synthetic?) it's all marketing term BS.  the only two true synthetics i know of are Amsoil, and the Mobile 1 full synthetic. I prefer Amsoil cause the have a one year/ 20K  guarantee, that means they will buy you a new engine if their oil F's it up before then.

also the best way to tell if it's a fake or not is to put it in a car that you know burns oil, if you see smoke coming out like normal. it's fake, if you don't see any, it's a real synthetic as natural gas burns clear an clean.  also NEVER buy Quaker State or Penzoil (same manufacturer) as they put paraffin wax in the oil, as do a lot of "high millage" oils which is why that is bad to. if anything, for a high millage vehicle, just get a heavier weight. my entire family has been using Amsoil for the past 15 years and have never lost an engine and our newest car is my '93 F150

Answer 6

High mileage.

Answer 7

Synthetic oil has a propensity to cause leaks in older motors. Personally with a vehicle that has 100k I would stay with organic oils.

Answer 8

Synthetic is always better it has better heat transferring properties. And you can go 7000 miles between oil changes because it evenly distributes the carbon throughout the oil unlike regular oil clumps up and sludges up.

Answer 9

If you are already using a synthetic oil, then stick with it, it is bad for your engine to switch from synthetic to conventional oil.  But if you are already using a conventional oil stick with it.  Just use the higher milage oil.