I have a 1985 Ford F-250 with a carbureted 460 V-8 that's become my daily driver for the next couple months. I purchased it in May and have run 15w-40 HDEO or SAE30 over the last several thousand miles. Now that temps have begun to get into the teens and soon to be single digits at night, it's time to find something thinner.
Not being fuel injected, it takes several seconds of cranking to get the engine fired up in extreme cold. It's clear the starter is not as happy when temps drop below about 15 degrees. My goal is to ease cranking (battery & electrical are fine), lessen cold start wear, and maybe gain some fuel economy.
The owners manual recommends practically any grade from straight 10W, all the way to 20w-50 depending on expected ambient temp. 10w-30/10w-40 are shown as the "all-season" oils, acceptable for 0F and up. 5w-20 & 5w-30 are shown as the cold weather viscosities for temps below 0, up to 60F. I suspect that 5w-20 will do better in cold and offer slightly better gas mileage.
That said, I've never run 5w-20 in any of my vehicles. I'm aware there's a sort of stigma against 5w-20 in older engines, but I don't suppose Ford would have listed that as an acceptable grade if it would cause problems.
My commute is 60 miles each way, so I can certainly use every last bit of fuel economy I can muster up. Truck has 100k miles and doesn't use / leak significant amounts of oil. It seeps some past old seals (rear main most likely), but I can't recall adding more than 1 quart in 3k miles. I'll be towing at least twice in the next couple months, but nothing too heavy that will stress the engine. I can't really think of anything that might make 5w-20 a poor choice. What do you think, is this a good / bad idea, or anything I'm missing?
Because of the flat tappet cam, I had QS Defy 5w-20 in mind, with a pint of STP Oil Treatment for a little extra ZDDP. QS Defy should be a heavy 20 weight if I'm not mistaken.
Not being fuel injected, it takes several seconds of cranking to get the engine fired up in extreme cold. It's clear the starter is not as happy when temps drop below about 15 degrees. My goal is to ease cranking (battery & electrical are fine), lessen cold start wear, and maybe gain some fuel economy.
The owners manual recommends practically any grade from straight 10W, all the way to 20w-50 depending on expected ambient temp. 10w-30/10w-40 are shown as the "all-season" oils, acceptable for 0F and up. 5w-20 & 5w-30 are shown as the cold weather viscosities for temps below 0, up to 60F. I suspect that 5w-20 will do better in cold and offer slightly better gas mileage.
That said, I've never run 5w-20 in any of my vehicles. I'm aware there's a sort of stigma against 5w-20 in older engines, but I don't suppose Ford would have listed that as an acceptable grade if it would cause problems.
My commute is 60 miles each way, so I can certainly use every last bit of fuel economy I can muster up. Truck has 100k miles and doesn't use / leak significant amounts of oil. It seeps some past old seals (rear main most likely), but I can't recall adding more than 1 quart in 3k miles. I'll be towing at least twice in the next couple months, but nothing too heavy that will stress the engine. I can't really think of anything that might make 5w-20 a poor choice. What do you think, is this a good / bad idea, or anything I'm missing?
Because of the flat tappet cam, I had QS Defy 5w-20 in mind, with a pint of STP Oil Treatment for a little extra ZDDP. QS Defy should be a heavy 20 weight if I'm not mistaken.
