This truck used to see 10-12,000 miles of highway only miles annually. It was pretty much only driven on the highway for the first 50k or so. Then engine was spotless until I started regularly short tripping it. I've been keeping it on synthetic because I thought it would be better for severe service like this engine sees. I think the question now is, would I be better off with a cheap conventional and changing it more often? Every 100 hours would be every 3-4 months for me, but not very many miles. I've thought a lot about how I should be determining my OCI, besides regular oil analysis. Some people use hours, others use fuel consumed. The following quote is from another thread:
Originally Posted By: MParr
I’ve used quiet a bit of Pennzoil and the brown baked on coloration is typical. Just look at the oil as it comes out of the bottle. If you like using conventional oil, switch to Valvoline, Motorcraft or Havoline. Change out the pvc valve and plumbing.
Lets assume that one hour of idle time equals 33 miles of driving, and that our average in motion speed is 33mph. Lets also assume that under normal intended operating conditions my truck would average 18 MPG. On my last OCI I went 185H, 2,559 miles, 201.2 Gallons burned, 13.8 MPH avg speed, 1.08 GPH avg. Assuming that my average in motion speed is 33 MPH and that 1 Hour of idle time = 33 miles of wear: My truck spent: 41.82% of it's run-time in motion, 77.37 hours, burned 142 gallons of fuel (1.83 GPH) 58.18% of it's run-time at idle, 107.63 hours, burned 59.2 gallons of fuel (0.55 GPH) So according to the Ford data, my oil had 2,559 actual miles on it and 3,552 equivalent miles of idle time wear on it. This means that my oil had the equivalent of 6,111 miles of wear on it. Another way that some people say you should determine your OCI is by the fuel consumed. My truck is rated to get 18/21 MPG(19.5 combined). Toyota states a 5,000 mile/6 month OCI. 5,000/18= 277.78 Gallons (1.83 GPH) (Assuming 33 MPH) 5000/19.5= 256.41 Gallons(1.69 GPH) (Assuming 33 MPH) 5,000/21= 238.1 Gallons (1.57 GPH) (Assuming 33 MPH) If I went 5,000 miles at 12.7 MPG I would have burned 393.7 gallons of fuel, that would be 362.32 hours at 13.8 MPH. If I changed my oil at 256.41 gallons burned at 12.7 mpg/13.8 MPH, that would give me a run-time of 235.97 hours/3,256.41 miles. I think on the Ford Superduty trucks they used recommend 3 months/5,000 miles, 200 engine hours or 250 gallons of fuel burned, whichever occurred first. This was for the diesel trucks with oil-fired injectors that were prone to shearing the oil down quickly. https://www.fleet.ford.com/truckbbas/non-html/DeiselTips/DLSIDLETIMESS.pdf
Originally Posted By: babbittd
Very interesting. http://www.government-fleet.com/article/...ive-idling.aspx According to research by Ford Motor Company, one hour of gasoline engine idle time equals 33 miles of driving.
Originally Posted By: oiltard
If I cruise at 60 for an hour (to make the numbers simple) vs. sitting in stop and go traffic for an hour and only going 10 miles, the mileage formula treats the latter as being 1/6th as much a factor in oil life usage, whereas the time formula at least treats them equally.