I have a '96 Maxima GLE, it had 200k when I got it. I've been doing 4-5k OCI's using whatever Autozone clearance oils I've had on the shelf. Castrol Edge 0w-30, Castrol Edge 0w-40, PUP 5w-40, PUP 0w-40, Chevron Supreme 10w-30, those are the ones I remember. Car has 235k now. I just changed the oil today with PUP 0w-40 (the SRT branded stuff) with a Hastings filter. I want to do a Blackstone oil analysis after this OCI, but I'm not sure when to end it. I want it to be representative of the OCI I'd like to do with a top-tier synthetic oil (7500 mi), but I don't want it to harm an engine of this age/mileage by going so long.
I did a compression test shortly after getting it, and I distinctly remember two cylinders being notably low (160-165 psi, vs 190-210 of the other four). So I imagine there's some blowby and other old-engine quirks that might foul up the engine oil more quickly than something newer with fewer miles. I should note that I do not have to add any oil in a 4-5k OCI. It's usually 3/4 qt. low when I drain it; I consider that acceptable and don't bother topping up in between OCIs.
Should I go the full 7,500 mi, or empty it sooner and have that tested before ramping up to 7500? Coming into the cooler season, I went with PUP 0w-40, as I understand it's not really a 40wt, but rather a 30 weight. 7,500 miles would have me changing/sampling in late February or thereabouts.
I did a compression test shortly after getting it, and I distinctly remember two cylinders being notably low (160-165 psi, vs 190-210 of the other four). So I imagine there's some blowby and other old-engine quirks that might foul up the engine oil more quickly than something newer with fewer miles. I should note that I do not have to add any oil in a 4-5k OCI. It's usually 3/4 qt. low when I drain it; I consider that acceptable and don't bother topping up in between OCIs.
Should I go the full 7,500 mi, or empty it sooner and have that tested before ramping up to 7500? Coming into the cooler season, I went with PUP 0w-40, as I understand it's not really a 40wt, but rather a 30 weight. 7,500 miles would have me changing/sampling in late February or thereabouts.