High Mileage Oil Vs. Mobil 1 Synthetic

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atijerino

atijerino

Joined
Jan 26, 2005
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Eagle, Idaho
What is the consensus or opinions of members of this on regards to using the High Mileage oils being offered nowadays versus using the Mobil 1 (10-40W) on a truck with more than 100K miles?
I have been using Castrol 10-30W high mileage oil in my truck and I used it in my FJ60. After reading many posting on this list I have been considering making the switch to Mobil 1 10-40W and want to know if there are any implications such as non-existing leaks or existing leaks getting worse after the switch.

Thanks,

_____________________________
Antonio '94 FZJ80
 
I can't help you, unfortunately, on the switch to Mobile 1, I can help shed a little light on the high mileage oil. From my understanding, high mileage oil has an additive in it that is basically brake fluid. This additive causes seals to swell up and can help to plug minor oil leaks... for a while. It is simply a bandaid used to cover up a problem that will raise its head again later. It doesn't do anything else to help reduce wear on a high mileage engine any more than any other dino oil. Synthetic oils (especially true synthetics, search other posts and the internet for more about this) will help reduce engine wear and also reduce the frequency of oil changes as it is superior in many aspects to dino oil.

I have not yet switched my 80 to syn yet as I have just recently purchased it. I can't give you any personal experiences. But, I will be switching to syn as soon as my truck needs its next oil change. :cheers:
 
my understanding on synthetic

with older vehicles is that the syn is more likely to create leaks.
 
I thought that the new syns were not supposed to cause leaky seals. But, after I switched over to Mobil 1, my engine started leaking like a sieve.
 
when i switched my '86 bus over to M1, I was driving down the NYS thruway, and oil was leaking on the exhaust pipes -- from somewhere --

-- shortly thereafter, it stopped, and hasn't leaked again --

-- and yes, i have checked the level since --

:D
 
Last edited:
Hey those 2 holes on top of the bus, are they the fresh air vents? ;) Cool!
 
they're cover for lights that used to be -- :D

i have replacements to put in -- just waiting on the weather --

:D

e
 
Synthetic is the way to go. If you do have a problem it will make it evident so that a fix can be obtained quickly.
 
wob said:
I thought that the new syns were not supposed to cause leaky seals. But, after I switched over to Mobil 1, my engine started leaking like a sieve.
Click to expand...

Isn't this normal?

I mean the oil is suspose to leak past old/bad seals and then expand them so the leak stops.

I read this somewhere on bobstheoilguy.com :D
 
seabeecruiser said:
I can't help you, unfortunately, on the switch to Mobile 1, I can help shed a little light on the high mileage oil. From my understanding, high mileage oil has an additive in it that is basically brake fluid. This additive causes seals to swell up and can help to plug minor oil leaks... for a while. It is simply a bandaid used to cover up a problem that will raise its head again later. It doesn't do anything else to help reduce wear on a high mileage engine any more than any other dino oil. Synthetic oils (especially true synthetics, search other posts and the internet for more about this) will help reduce engine wear and also reduce the frequency of oil changes as it is superior in many aspects to dino oil.

I have not yet switched my 80 to syn yet as I have just recently purchased it. I can't give you any personal experiences. But, I will be switching to syn as soon as my truck needs its next oil change. :cheers:
Click to expand...


I use Mobil HM 10W30 Semi-Synth (here in South Florida) and it's the right oil for my rig as the miles gracefully accumulate. To me, it may the "training wheel" step to full synthetic. I've owned her since new - 127k and she's clean. I don't believe in adding anything to the oil either- (never have except for the Rislone I used to put in the L82 Vette I drove in college :flipoff2: ). And I respectfully disagree :eek: with seabee that it's basically a brakefluid-like additive. There are numerous reports/tests on this new generation of HM oil and Mobil is probably the best - or among the best. Search for cary on this sight or Google high mileage oil, semi synthetic or try here for starters: http://news.thomasnet.com/fullstory/21141
Good luck!
 
I switched to M1 0w40 at about 225,000mi and the motor would suck the M1 when reving the motor to high rpms.
I switched to RotellaT 5w40 and the leaks I had stopped leaking and I can rev the motor as high as I want with no oil sucking.
 
Kurt,

I have low idle pressure on the 97 - what's your hot idle oil pressure these days? Mines at the bottom of the gauge.

DougM
 
Eric- sweet bus, man. I made the switch to M1 0w40 at 124K, no leaks at 129 no, just changed it again. My oil pressure is definitely low at warm idle, but goes up quick as soon as the light turns green, I'm not worried about it. synthetic good, high mileage oil bad, imo.
 
2badfjs said:
with older vehicles is that the syn is more likely to create leaks.
Click to expand...

IF that's true, then you have engine problems that NEED to be addressed anyway.

Use Mobile one synthetic. Then install a bypass filter and run that oil 10,000+ miles. You make up the cost of the synthetic oil in the length of use you get out if it.

Ive been using Amsoil heavy duty diesel oil in my (three) diesel rigs forever. Ive used by pass filters the entire time. I send in oil analysis samples and only change my oil when the LABRATORY tells me too. I change my standard filter every 3,000 miles. Ive been averaging above 15,000 miles between changes.

Good synthetic oil (Amsoil Mobil) today are spectacular. The issue in changes is the oil filter. If you dont change your filter every 3000 miles you risk it getting clogged and going into bypass mode.

Bypass filters

Bypass filter 2
 
IdahoDoug said:
Kurt,

I have low idle pressure on the 97 - what's your hot idle oil pressure these days? Mines at the bottom of the gauge.

DougM
Click to expand...
Cruising on the highway at ~65mph, the oil pressure guage sits a little below the half-way point.

I'm currently using Mobil1 10-30.
 
Doug, there are 4 marks on the guage. The bottom(first mark) is low and top (forth mark) is high. That leaves the two makes in the middle. Mine moves between the two in the middle.
At idle it on the 2nd mark and when driving its at the 3rd mark.

I did replace the spring and valve in the oil pump that Robbie was takling about some time ago but it didn't change anything.
 
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