High mileage oil with new seals?

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31
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USA
Hello folks: I have recently acquired my fathers old truck, a 2002 5.3 Silverado. Truck is closing in on 250k, and is nearing an oil change. I have been contemplating what oil I should go with. I was debating on if I should go with a high mileage oil, or just use a good name brand synthetic. The truck won't be a daily driver, but I would like to keep it in the best running shape possible as there is a lot of nostalgia attached to it. Most of the driving it will see will be just local backgrounds and occasional trips to town. I was considering using a high mileage 5w-30 thinking it would be beneficial to the 250k motor. However, I am hesitant because my father just had all new seals put on (valve covers, oil pan, rear main, even o-ring on dipstick tube) less than 10k miles ago. Would there be any benefit to using a high mileage oil with all new seals? Any risk in using high mileage on new seals because of the conditioners or swelling agents? Aside from seal conditioners, are there any extra additives to high mileage oils compared to their non HM synthetic brothers? I ask this because on a bottle of mobil 1 high mileage I had in the garage, the star chart on the back claims it protects "high engine temperatures" better than regular mobil 1 Any high mileage oils that offer good protection without attempting to swell seals? If high mileage is not the route to go, what is a good synthetic for a high mileage vehicle? Best filter for high mileage 5.3's? Also, if it matters, my father wasn't an oil stickler like I am. The truck has probably seen conventional oil for 90% of its life. Should I stick with the conventional if that is what it is use to? The truck doesn't burn or consume any oil as far as I am aware, but I have only had it for 4k miles. If it does burn or consume, it is very minimal. Thanks for any input and advice in advance.
 
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4,672
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MN
Pat Goss doesn't know diddly-squat in his video. No worries. Here is why: The SN spec rating, and also piled on more in the dexos1 spec if it has that too, already has a test where they make sure different kinds of elastomers (seals, rubber type junk) don't swell too much, or shrink also! So High Mileage oils may have a small amount of extra seal conditioning, but the SN and/or dexos1 rating tells you it will be fine, not too much, not too little..... Its on page 19 of the following PDF file, or you can Ctrl-F search on the word elastomer in the document for all occurences of those kinds of important tests: https://www.aftonchemical.com/Afton/media/PdfFiles/Afton-Chemical-Spec-Handbook-September-2019.pdf
 
Last edited:
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4,672
Location
MN
Originally Posted by CT8
What are the approvals on the oils you are buying? That will tell you all..
Whether its SL, SM, SN, or SN+, they have to pass those elastomer tests. Since those tests demand they not swell too much, High Mileage oils have a slight bias toward pliability, not swelling, as explained in: "Seal Conditioners: Also often esters, seal conditioners are potent additives used in small dosages and designed to keep seals pliable. These are especially important for highly paraffinic base oils such as Group IIIs or PAOs due to the tendency of these base oils to shrink and harden seals." -- https://www.bobistheoilguy.com/whats-in-your-motor-oil/
 

Floyd1

Thread starter
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31
Location
USA
Originally Posted by oil_film_movies
Originally Posted by CT8
What are the approvals on the oils you are buying? That will tell you all..
Whether its SL, SM, SN, or SN+, they have to pass those elastomer tests. Since those tests demand they not swell too much, High Mileage oils have a slight bias toward pliability, not swelling, as explained in: "Seal Conditioners: Also often esters, seal conditioners are potent additives used in small dosages and designed to keep seals pliable. These are especially important for highly paraffinic base oils such as Group IIIs or PAOs due to the tendency of these base oils to shrink and harden seals." -- https://www.bobistheoilguy.com/whats-in-your-motor-oil/
I typically just run whatever name brand synthetic I can get the cheapest in my other vehicles-- mobil 1, PP, even SuperTech from time to time. Guess I am just being picky with this application because I want to feel extra "positive" I am choosing the best oil for 250k motor
 
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1,679
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South Carolina
I have a 2002 Tahoe with the 5.3L at 247k miles. I'm still on the original seals, no leaks, and use Driven LS30 5w-30 which is PAO oil with 8% ester. I wouldn't worry about a high mileage oil. The Havoline 6 quart box of Pro DS from Walmart for $19.97 and a Fram Ultra XG9837 filter would square you away for 7,500 mile OCIs.
 

MolaKule

Staff member
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21,688
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Iowegia - USA
Originally Posted by Floyd1
Hello folks: ...I was considering using a high mileage 5w-30 thinking it would be beneficial to the 250k motor. However, I am hesitant because my father just had all new seals put on (valve covers, oil pan, rear main, even o-ring on dipstick tube) less than 10k miles ago. Would there be any benefit to using a high mileage oil with all new seals? Any risk in using high mileage on new seals because of the conditioners or swelling agents?... Aside from seal conditioners, are there any extra additives to high mileage oils compared to their non HM synthetic brothers? I ask this because on a bottle of mobil 1 high mileage I had in the garage, the star chart on the back claims it protects "high engine temperatures" better than regular mobil 1... Thanks for any input and advice in advance.
As explained below for these components, HM oils have no effect on valve covers (Gasket), oil pan (Gasket), and even o-ring on dipstick tubes, so an HM oil will neither help nor hurt those components. It will keep the rear main seal and valve-stem seals pliable. and will clean the engine a tad better. However, if the compression is ok, if there is no smoke on start-up, and if the engine is in otherwise good shape, changing oil at Severe Service intervals using just about any modern oil should work just fine.
Quote
When discussing seals such as in engines, transmissions, and other driveline components, the context is that of using flexible, elastomeric materials to akeep fluids contained within the mechanical system that have rotating components exiting the system, such as protruding rotating shafts. For a gasket, the context is that of using a material (such as silicone or cork or composite), or some other material to keep fluids contained in and around stationary objects, such as the valve cover gasket on an engine or the pan gasket on an automatic transmission. Both seals and gaskets "prevent" loss of fluids... Conditioning seals refers to the following actions: 1) Increasing seal pliability due to Seal elastomer molecular replacement 2) Seal cleaning, Today's synthetic formulations have pretty much solved the seal "shrink-swell" problem. Stop leak fluids have little effect on Gaskets, so if you have a leak to the outside, it is usually due to a Gasket, not a Seal. Now on older vehicles or vehicles with rear wheel drives, the most common fluid leak occurs because of a worn tailshaft seal, and is mostly seen when parking on an upslope where the rear of the vehicle is below the front. On front wheel drive vehicles, the most common fluid leak is due to the pan gasket, in my experience.
 
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Kentucky
I personally feel the purported benefits of HM oil to be mostly marketing, and indistinguishable from standard oils in practice. That's been my experience. I generally buy my oil only when on sale or closeout, so using HM oil would mean waiting for a HM oil to come on sale (seldom) or switching back and forth between HM oil and regular oil to catch good sales/closeouts. I don't want to switch back and forth, so I just use regular oil which I can almost always find top-tier oil at bargain prices. None of my high mileage (all of them!) vehicles seem to complain about not having high mileage oil, none use oil excessively, so why bother?
 
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3,649
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St. Charles County, Missouri
Wish we could retire the OldPat video. Perfectly ok to use HM. I would if I could pick it up at same price, which I could if I changed my own but it's worth only a few bucks at an oil change place and the added cost is usually too much for me.
 
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145
Location
Idaho
What oil did your father run in the old 5.3 to get it this far? I suspect you can keep using whatever he's been using for the last 250k miles as long as it meets whatever specification the owner's manual states - which really only calls for an API certified oil in a 5w or 10w30 grade. I will echo what has been said - a HM will certainly not hurt anything, nor will a "non-HM" oil. I would buy any name brand oil you can easily obtain on sale or with rebates. I personally am a fan of the Havoline Smart Change 6qt box, which is great for these LS truck engines of this era that take 6 quarts to change. They have a conventional, HM synthetic blend, or a full synthetic available at Walmart. It's really up to you. I think it's member DNewton who says the act of maintenance is more important than the type of lube you use.
 
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1,061
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Florida /Texas
I agree with the vid, as that's my experience, don't switch a high mileage vehicles oil, unless leaks or oil consumption is at a point that there's no choice. Cause these oils can actually create leaks on a motor that doesn't have an issue , cause they do soften and swell rubber seals and gaskets.
 
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3,649
Location
St. Charles County, Missouri
Originally Posted by Mackelroy
I agree with the vid, as that's my experience, don't switch a high mileage vehicles oil, unless leaks or oil consumption is at a point that there's no choice. Cause these oils can actually create leaks on a motor that doesn't have an issue , cause they do soften and swell rubber seals and gaskets.
Disagree completely.
 
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6,884
Location
Wet side WA
Originally Posted by Mackelroy
I agree with the vid, as that's my experience, don't switch a high mileage vehicles oil, unless leaks or oil consumption is at a point that there's no choice. Cause these oils can actually create leaks on a motor that doesn't have an issue , cause they do soften and swell rubber seals and gaskets.
I've used HM oil in my Corolla off and on for 70K miles plus 3 or 4 times. No ill effects. Yes I buy what's on sale sometimes HM is cheaper like this was.

Pennzoil HM.jpg
 
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3,649
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St. Charles County, Missouri
All SN oils have Group III, if there's a little extra group III they charge more and call it semi-syn. All SN oils have seal conditioners, if there's a little extra seal conditioner they charge more and call it high mileage.
 
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1,399
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Dallas Texas Area
Originally Posted by RDY4WAR
I have a 2002 Tahoe with the 5.3L at 247k miles. I'm still on the original seals, no leaks, and use Driven LS30 5w-30 which is PAO oil with 8% ester. I wouldn't worry about a high mileage oil. The Havoline 6 quart box of Pro DS from Walmart for $19.97 and a Fram Ultra XG9837 filter would square you away for 7,500 mile OCIs.
Have 3 GMT800 trucks in my sig with that engine code "T" LS engine and been using XG3675 all good Dave
 
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