Dayton Daily News

Wheels: Bruce from Florida writes, “I have a Ford Ranger Super Cab and the tire size is P225/70X15. Can I use P215/70X15 tires that I have in the garage from another vehicle? Will this change the speedometer reading? Should I stay with the original-size tires?

Halderman: It is always the best policy to use the exact same-size tires that come with the vehicle from the factory. The major consideration is the overall outside diameter of the tire. From a practical point of view, a tire that is 10 mm larger or smaller could be used without too much trouble. Therefore, you could use the P215/70X15 instead of the original P225/70X15. However, there is another fact to consider since this is being used on a truck. With the smaller the tire size, the load capacity is less. Therefore, the tire may be overloaded if the truck is loaded.

Regarding how much difference the change of tire size makes to the speedometer readings, I go to: www.miata.net/garage/tirecalc.html.

Wheels: What if Bruce wants to install larger-diameter wheels on his truck? What factors should he consider?

Halderman: Besides the wheel width and offset, the major factor that should be adhered to is that the overall diameter of the tire/wheel combination should be the same as the original. This means that as the wheel diameter increases, the aspect ratio of the tire has to decrease in order to maintain the original outside diameter. For example, Bruce could elect to purchase 16-inch diameter wheels that fit his truck and use P245/60X16 tires. However, he would have to check that the larger wheels and tires fit into the wheel well without rubbing on a suspension, body or steering component.

Wheels: An e-mail from Fred says, “In a discussion group I follow on www.Edmunds.com, the Honda owners swear that the oil can’t be changed until the 10,000 or 7,500 miles recommended in their owner’s manual because Honda has ‘special’ break-in oil. What do you know about the special break-in oil? Does Honda do something special?”

Halderman: What you are reading is correct and Honda/Acura even states in the owner’s manual not to change the engine oil before the first scheduled interval.

What is in the factory fill I do not know, but I think they (Honda) want the engine to break in before using an oil with a lower coefficient of friction, which could delay the normal break-in wear pattern.

What would I do? I would follow the owner’s manual recommendation and not change the oil until the normal interval based on your driving habits (highway compared to short city-type driving).

If you are planning to switch to synthetic oil, I would recommend that you use conventional oil at the first change and then switch to synthetic at the next oil change. This is what I normally do.

James D. Halderman is an ASE-certified master technician, a member of the Society of Automotive Engineers and the author of 12 textbooks. Submit your automotive care questions to Halderman via e-mail at jhalderman2@juno.com, or write him in care of: Wheels, Marketing Publications Department, Dayton Daily News, 45 S. Ludlow St., Dayton OH 45402.