using M1 High Mileage... having doubts, switch?

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Aug 14, 2014
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I recently purchased a 2001 Infiniti QX4 with 124,000 miles in July from a used car dealership. The car manual recommends 5w30. At the time, I thought it would be best to switch it to synthetic (mainly because I do not know the history of the car and I hear this oil is better?) high mileage oil and change frequently a couple of times. I just started developing a leak with the oil cooler gasket. I realize this could be coincidence or encouraged from the oil; research shows this is a common nissan problem around 120k and it is a simple cheap fix. The issue now is I'm worried about other leaks developing; I have about 4,000 miles in with this oil, should i switch to regular Mobil 1? a conventional oil? I would like to clean out this possibly neglected engine, but now I'm just paranoid! Help!!! EDIT: I also have a 1991 Honda Civic LX that I just purchased for gas purposes. It is extremely low miles for its year (125,000) and calls for 5w30? Ideas for this one? I had planned on using the M1 HM oil, but now I don't know. I would like to keep the oil the same if I can and if it's recommended. I greatly appreciate any feedback for my concerns. Thank You!!!!
 
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Joined
Jun 28, 2005
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If you want to clean the engine you'll have to stay with synthetic for maximum benefits and take your chances with other gaskets leaking. Valvoline maxlife is a great high mileage oil that you can get in semi synthetic that may be a good middle ground for you.
 
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Oct 1, 2010
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I would not blame the developing oil leak on the M1 HM. High Mileage oils contain additives that soften and swell seals, reducing or eliminating leaks from seals that have hardened and shrunk over the years. But HM oils can't work miracles. If a seal is cracked, the oil can't fix that, so it must be replaced. How long have you had the QX4? Is it possible that the leak has always been there, but you are just noticing it for the first time? It can take a while to find all the issues present in a used car after you first buy it. About the Honda: I say run the M1 HM 5w30 in it also.
 
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I use M1 HM in my Equinox and love it. Engine is quiet and the minor oil burning I had was gone after my first oil change.
 
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I'd fix the gasket leak and continue with M1 HM for two reasons: 1) M1 HM is a terrific product. Its SLrating is what your Ininiti was spec'd for when new. And talking to the M1 tech support guys, it seems that M1 HM's hgiher additive level makes it one of their internal favorites. 2) The seal conditioners in a HM oil are beneficial to an engine that is getting on in years. Seals do lose pliability over time and HM oils can help avoid future leaks as well as mitigate current ones.
 
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So many people on here opt to use the HM oil too early in my opinion. Yes, you can use it even in a new car, but it's certainly not optimal with so many other choices. If the car is well cared for (maintenance records, etc..) I don't see a reason to use the HM at this point. I would fix the known issue and continue to drive with a good high-quality synthetic oil. I would cross the HM bridge when you come to it.
 
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Originally Posted By: Danh
I'd fix the gasket leak and continue with M1 HM for two reasons: 1) M1 HM is a terrific product. Its SLrating is what your Ininiti was spec'd for when new. And talking to the M1 tech support guys, it seems that M1 HM's hgiher additive level makes it one of their internal favorites. 2) The seal conditioners in a HM oil are beneficial to an engine that is getting on in years. Seals do lose pliability over time and HM oils can help avoid future leaks as well as mitigate current ones.
You make some really good points there. The SL rating always cautioned me about that oil. Why isn't it SN like the MaxLife Synthetic? The older designation leads me to believe that the oil is in some way inferior to a SN oil. Am I wrong?
 
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Originally Posted By: CELICA_XX
The SL rating always cautioned me about that oil. Why isn't it SN like the MaxLife Synthetic?
If I were to venture a guess, it would be that phosphorous content would preclude SM or SN certification.
 
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Originally Posted By: Garak
Originally Posted By: CELICA_XX
The SL rating always cautioned me about that oil. Why isn't it SN like the MaxLife Synthetic?
If I were to venture a guess, it would be that phosphorous content would preclude SM or SN certification.
I agree the extra phosphorous is the reason. In an oil-burning engine, phosphorous has the potential to poison the catalytic converter. As I understand it, the proliferation of lighter oils in the early 2000s lead to a concern that oil consumption would increase, so phosphorus was limited in SM and later SAE standards. Phosphorous is generally a good thing in motor oil, provided it doesn't burn it excessively.
 
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