Is there any issue with using high mileage oil in a low mileage motor?

Michigan TJ

Michigan TJ

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Yes, again. I’m new here and want to get this right. I’ve read a couple threads here on high mileage oil for “older engines” vs synthetic oil. My 2003 TJ has 54,340 miles. Just bought it right before Christmas. Now I realize this isn’t high mileage, but it is an older engine. I’m going to change the oil soon and not sure which oil to use. I’m a believer in synthetic oil, I use it in my truck, car, and bike. But they are newer vehicles. The TJ has no leaks, but I’m wondering because the engine is 18 years old, maybe the seals are not at their best any longer. I don’t know what oil is in it now. Is there any issue with using high mileage oil in a low mileage motor? Let me know what you think.
 
cliffish said:
It keeps the seals conditioned, usually these engines have a slight RMS seal leak and it helps. If you threw in synthetic oil you might find you have a rms leak as the synthetic molecules will find their way through faster than conventional oil.
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Thanks. From reading the threads here, that seems to be the consensus.
 
You're correct in your thinking, regardless of the mileage the seals have been in the engine for 18 years. older engines don't like synthetic, it makes them leak. A good high mileage multi vis oil, maybe 10W30, might work for you. I use 10w30 high mileage Pennz in my old vehicles, but I live in a much warmer climate than you.
 
WesTex TJ said:
You're correct in your thinking, regardless of the mileage the seals have been in the engine for 18 years. older engines don't like synthetic, it makes them leak. A good high mileage multi vis oil, maybe 10W30, might work for you. I use 10w30 high mileage Pennz in my old vehicles, but I live in a much warmer climate than you.
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Thanks. I was thinking of using 5W30 no matter which oil I used.
 
Just a FYI for those wringing their hands about using synthetic because they think their engines won't last as long with a conventional. With proper oil and filter changes at appropriate intervals it doesn't matter which you use or what brand... all of today's modern engine oils are SUPERB.

And for us older guys, we remember both Mercedes Benz and Volvo were advertising heavily back in the 50's and early 60's about their engines lasting over a million miles. Guess what engine oils they were running? I'll give you one guess and it wasn't synthetic.

I choose to run a conventional because I live in a temperate climate. When would I choose to run a synthetic? I would during the winter if I lived in an extreme-cold area like Minnesota, North Dakota, Alaska, etc. Synthetic is proven and well known to flow better in extreme cold conditions. But for where I live here in SoCal, I choose to run nothing more exotic than a 10W-30 conventional. I'd happily run Valvoline, Castrol, Mobil, NAPA (made by Valvoline), Pennzoil, etc. And yes I run a High Mileage just to keep all the seals in good condition.
 
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Jerry Bransford said:
Just a FYI for those wringing their hands about using synthetic because they think their engines won't last as long with a conventional. With proper oil and filter changes at appropriate intervals it doesn't matter which you use or what brand... all of today's modern engine oils are SUPERB.

And for us older guys, we remember both Mercedes Benz and Volvo were advertising heavily back in the 50's and early 60's about their engines lasting over a million miles. Guess what engine oils they were running? I'll give you one guess and it wasn't synthetic.

I choose to run a conventional because I live in a temperate climate. When would I choose to run a synthetic? I would during the winter if I lived in an extreme-cold area like Minnesota, North Dakota, Alaska, etc. Synthetic is proven and well known to flow better in extreme cold conditions. But for where I live here in SoCal, I choose to run nothing more exotic than a 10W-30 conventional. I'd happily run Valvoline, Castrol, Mobil, NAPA (made by Valvoline), Pennzoil, etc. And yes I run a High Mileage just to keep all the seals in good condition.
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Thanks, Jerry. I’ve decided I’m going to use the high mileage oil. I like Valvoline and Mobil 1. Thanks everyone for your input.
 
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I don‘t know - all the reading I’ve been doing about our Jeep’s and the 1990 Chevrolet 454TBI P30 chassis under the motorhome we acquired a couple of years ago with 17k miles on it - somehow I came to the conclusion that synthetic was OK.
Last change last Summer, I went synthetic. Jeep has 122k on it. No leaks that I’ve seen in the driveway. The motorhome? I’ve got some drips, but not sure that it isn’t front Seal on tranny as what fluid i can catch off the bottom of the tranny pan is red.

So now, maybe I’m confused and lucky.
 
The best uses for synthetic are in small air cooled engines like lawnmowers and generators. Also in engines that see constant high rpms. Regular old dino oil is more than adequate for most any liquid cooled engine operating at lower rpms. Every few years they increase the ratings of oil for new engines which improves the oil for the rest of the older engines out there. Comparing today's oils to oils just s decade or two ago shows the improvement the manufacturers have made.
There are some engines that the manufacturer states the use of synthetic oil, but it just isn't necessary for the vast majority of engines, and certainly not in our old TJs.
 
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Michigan TJ said:
Thanks, Jerry. I’ve decided I’m going to use the high mileage oil. I like Valvoline and Mobil 1. Thanks everyone for your input.
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Good call. Even though the miles are low, the seals are 18+ years old and, obviously, see infrequent oiling!
 
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Maybe I’m looking in the wrong universe, but I can’t find Valvoline high mileage conventional oil, only synthetic blend. Valvoline doesn’t even have it listed on their website. Maybe I’ll just get the synthetic blend and be done with it?
 
Michigan TJ said:
Maybe I’m looking in the wrong universe, but I can’t find Valvoline high mileage conventional oil, only synthetic blend. Valvoline doesn’t even have it listed on their website. Maybe I’ll just get the synthetic blend and be done with it?
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Use any major brand of high mileage conventional.
 
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