HM Syn Oil Recommendation.

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May 4, 2024
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Bought a '99 Accord 2.3 in good shape, 114 k miles. I'm going to use a HM Syn Oil. Do any brand(s) stand out for a 25 year old engine? How do the additive formulas differ?

Thanks

Adam
 
Bought a '99 Accord 2.3 in good shape, 114 k miles. I'm going to use a HM Syn Oil. Do any brand(s) stand out for a 25 year old engine? How do the additive formulas differ?

Thanks

Adam
Who knows what the "additive formulas" are? How would we know?
 
High Mileage oil just have more seal conditioners than non High Mileage oils. Seal conditioners can sometimes reduce leaks or prevent leaks from happening for longer. Some believe that High Mileage oils will also be at the thicker side of whatever viscosity grade they are in but looking at data sheets I've seen the High Mileage version's be thinner sometimes. For the most part they're similar from one brand to another. If it was mine I'd probably just use supertech 5/10w-30 High Mileage. I don't know if they have 10w-40 in High Mileage anymore but that would also be an option. If it doesn't leak I'd see myself using 15w40 as well.
 
Who knows what the "additive formulas" are? How would we know?
The high
High Mileage oil just have more seal conditioners than non High Mileage oils. Seal conditioners can sometimes reduce leaks or prevent leaks from happening for longer. Some believe that High Mileage oils will also be at the thicker side of whatever viscosity grade they are in but looking at data sheets I've seen the High Mileage version's be thinner sometimes. For the most part they're similar from one brand to another. If it was mine I'd probably just use supertech 5/10w-30 High Mileage. I don't know if they have 10w-40 in High Mileage anymore but that would also be an option. If it doesn't leak I'd see myself using 15w40 as well.
I've also noticed that High Mileage Full Synthetic oils tend to have more phosphorous and zinc (anti-wear) additives and more calcium (detergent) additives than their non high mileage full synthetic couterparts of the same brand.
 
High Mileage oils have two properties typically. An additive to swell seals and stop leaks. Thicker in their weight class.

Except for rear main I would repair any other gasket or seal that was leaking.

Unless it's burning oil I don't see a need for thicker oil.

It's a 25 year old vehicle. I would not get carried away on the oil.
 
I used to use a lot of the Valvoline Syn. On your Accord, anything will work. The Costco Kirkland 5w30 is an economic choice that offers a lot of value. I keep Quaker State Synthetic on the shelf as well.
 
@Ant57
FWIW, for the cost it's difficult to beat Super Tech FS HM IMO.

I've had good luck with Mobil 1 & Citgo as well...

Just my $0.02
 
I have had great results with Valvoline Maxlife in the past. Maybe I am lucky. One instance of a stuck ring=unstuck, and one instance of a seal leak=stopped the leak, for a while at least.

This is with the "synthetic blend".
 
High Mileage oils have two properties typically. An additive to swell seals and stop leaks. Thicker in their weight class.

Except for rear main I would repair any other gasket or seal that was leaking.

Unless it's burning oil I don't see a need for thicker oil.

It's a 25 year old vehicle. I would not get carried away on the oil.

Agree with this. All of it. Including the don’t use it unless you see some burning or leaking.
 
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