Is there any oils that are full synthetic for high mileage cars? I see Valvoline makes a high mileage blend but I want all synthetic with seal additives. Also was wondering if any high mileage oil is capable of going 10,000 miles? I will be using this in a 1988 Suburban that has seen 10k oci's with Mobil 1 since it was new and nothing else. I am however starting to use a little more oil because of small leaks, it use to use 2qts every 10k and now I am up to about 3qts every 10k, I know that is not bad for a motor with 300k on it but the motor is tight and runs great so if I can avoid taking it out just to replace seals and gaskets by using an oil with additives I would like to try that first.
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