Thursday, March 15, 2012

Tire Pressure, part 2

Part 1 here. The owner of a tire store came into the liquor store where I work, and I struck up a conversation with him. I asked him if I should follow the tire sidewall (44 psi) or the driver's door (35 psi) recommendation. He said if I put in the max pressure, the tires will wear out in the center, so I should use 35 psi. It will be a smoother ride with better MPG, and the tires will last longer. The only time I should use max tire pressure is if I have a heavy cargo load, which I rarely do. I don't even have the middle and back seats in the van.

This is a different opinion from my mechanic (who also services tires) who said I should use the tire sidewall recommendation for longer tire life and better MPG. So now I have two knowledgeable people with different views on tire pressure.

Should I stick with 35 psi, inflate to 42-44 psi, or split the difference and go with 37-39 psi?

Wednesday, March 14, 2012

Gas and Tire Pressure

Another fill-up using 91 octane at a Sinclair station:

March 13:
261.8 miles / 14.032 gallons = 18.66 mpg

I don't know what to think about this stat. On one hand, it's pretty good mileage for winter. But on the other hand, it's been a mild winter, and it's 91 octane! 91 octane was $3.909 a gallon. If I don't start seeing 22+ mpg with 91 octane, I'm going back to 87 octane at a Cenex station.

One possible reason for the lower-than-expected mileage would be the tire pressure on the new tires I recently purchased. I like to have my tires at 40-44 psi (max load on tire sidewall is 44 psi). The mechanic or technician might have set the tires at 35 psi, which is what the tire pressure placard on the driver's door recommends.

(5 minute break)

I just went outside and checked the tire pressure, and the tires were indeed set at 35 psi. Boy, the one time I go to a different mechanic...

Yes, the ride is a little smoother at 35 psi, but I'd rather have higher MPG and longer tire life (more even tire wear at 40-44 psi).

Caravan odometer = 178,422 miles