I've been doing oil changes on my own vehicles for 30 years now, and just experienced something that disturbed me a little.
I've been using Wix filters now for 15 or 20 years, and as far as I know, they're great filters. On my Tahoe, I noticed that the oil pressure dropped earlier this spring. After I did an oil change I noticed a lot of sludge in the oil after switching to Valvoline synthetic. After changing the oil/filter, the oil pressure returned to normal. A couple of months later, before the next oil change was due, I noticed the oil pressure dropping again. I changed the oil filter again, and the oil pressure returned to normal, once again. Only this time, I didn't have access to a Wix, so I had to use another brand. This time I wasn't losing any oil pressure, or very little, even when it was time to change my oil again this month. When I removed the drain plug, the oil wouldn't even come out right away, and came out in globs! It was all sludged up, but I wasn't losing oil pressure.
I figure that the Wix does not have a bypass valve, so when the filter gets plugged up with sludged oil, the pressure drops giving you warning that something needs attention ASAP. This other brand of filter had a bypass valve and allowed the sludge to pass straight through, all over my valve train and everything.
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I had never thought of the cons to having a bypass valve until today. I will now always keep a stock of a few Wix filters (or ACDelco, or other decent brand that does not have a bypass filter). If I see the pressure dropping, I know to change the oil pronto, even if the usual oil change interval has not yet passed.
I've been using Wix filters now for 15 or 20 years, and as far as I know, they're great filters. On my Tahoe, I noticed that the oil pressure dropped earlier this spring. After I did an oil change I noticed a lot of sludge in the oil after switching to Valvoline synthetic. After changing the oil/filter, the oil pressure returned to normal. A couple of months later, before the next oil change was due, I noticed the oil pressure dropping again. I changed the oil filter again, and the oil pressure returned to normal, once again. Only this time, I didn't have access to a Wix, so I had to use another brand. This time I wasn't losing any oil pressure, or very little, even when it was time to change my oil again this month. When I removed the drain plug, the oil wouldn't even come out right away, and came out in globs! It was all sludged up, but I wasn't losing oil pressure.
I figure that the Wix does not have a bypass valve, so when the filter gets plugged up with sludged oil, the pressure drops giving you warning that something needs attention ASAP. This other brand of filter had a bypass valve and allowed the sludge to pass straight through, all over my valve train and everything.
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I had never thought of the cons to having a bypass valve until today. I will now always keep a stock of a few Wix filters (or ACDelco, or other decent brand that does not have a bypass filter). If I see the pressure dropping, I know to change the oil pronto, even if the usual oil change interval has not yet passed.