Maintenance Q&A
Treating fuel and taking care of tires

By Paul Abelson, Land Line senior technical editor

I've had some cold-morning starting problems. My 2012 Volvo has a D12 and only 312,000 miles. I haul everything from grain and feed to farm and industrial equipment. I used a fuel additive, but I'd like one that does everything I need to keep going all year, even in Iowa winters. What's the best additive for that? Is there one that gets everything done?

First of all, Land Line doesn't recommend or endorse individual products by brand name. With fuel additives, we'd need to be a Consumer Reports-type organization, complete with laboratories and technicians to test all the products that are out there.

Different additives do different things well. Some do specific things better than others.

That said, I would select from among the major brands that have stood the test of time. You are probably familiar with the brands seen at truck stops and in parts stores. Howes, Power Service, FPPF, Lucas and Penray are a few that come to mind. The EPA has a list of all registered fuel additives (EPA does not approve nor disapprove). I stopped counting at more than 200 and I was only up to "F" in the alphabetical listing.

What do you want your additive to do? It can:

Delay gelling. When temperatures drop too low, waxes in the fuel separate and link up to form a matrix that restricts flow much the way a honeycomb holds honey. If fuel cannot flow, the truck cannot start. If it is running, it stalls. Most additives block the free wax from linking, lowering the gelling temperature.

Control water. Some emulsify or encapsulate it by breaking it into tiny droplets that pass harmlessly through the fuel system. Others de-emulsify water, so it precipitates out of the fuel. (Periodically drain your fuel-water separator and your fuel tank.) Water can collect in fuel lines, freeze, and block fuel flow.

Lubricate the fuel system if needed, keeping components operating freely.

Protect against corrosion and leave a protective coating on clean, bare metal.

Increase the cetane index, a measure of how easily an engine can start when cold.

Control bacteria and fungus growth. That protects fuel tanks and extends the life of fuel filters. Some do it by creating a barrier between fuel and water, so the organics cannot get nutrients from fuel or oxygen from water. Others contain EPA-registered pesticides, to be used once or twice a year. They must be used only according to label directions.

Clean the fuel system, keeping fuel flowing through injectors.

Most additives do many of these tasks, some to a greater and some to a lesser degree. No one does everything 100 percent. Some are good general additives. Some do a few tasks excellently.

When deciding on an additive to use, read the information on the package or the web. Prioritize the results you're after. Check how each product matches your needs. What's best for a driver who operates where temperatures rarely reach lower than 10 degrees may not work when they drop to minus 20 degrees. Don't blend them. You can switch experimentally, but in different fuel loads, and you should watch for unintended consequences.

I read your tire article and searched for the information. I couldn't find a chart to determine correct tire pressure for my 1998 Freightliner straight truck (20-foot box with 60-inch sleeper) with a large lift gate. I run Double Coin tires. It's used to haul company equipment to job sites. The front weighs 8,500 pounds and the rear single axle (four tires) scales in at 16,500. The rears are maintained at 110 psi using Cats Eyes. The fronts were increased to 114 psi from 100 psi after noticing tread wear on the edges. I do not drive in winter months and travel about 12,000 miles per year. Any suggestions?

I went to Double Coin's web pages. They have load-inflation tables for all their tires. (bit.ly/tirechart)

Your two steer tires carry 4,250 pounds each, far less than the 6,000 OTR trucks carry per tire. Your single drive axle carries almost as much weight as those who run over the road at 80,000 pounds. Their tandems put down 17,000 pounds per axle and you put just 500 less, or 4,125 per tire. An 18-wheeler carries 4,250 per tire.

The 295/75R22.5 is a hefty tire. In the table, we find that 70 psi will support 4,500 pounds on each of the steer tires. And 75 psi will safely support 4,725 pounds on the drives.

Inflating to 75 psi in each drive tire supports 4,300 pounds each, or 17,200 on the axle. That gives a 700-pound margin on the drive axle.

Reducing pressures to 70 and 75 psi, or even going to 75 psi all around will give you a more comfortable ride and will help your tires last longer. I suggest replacing your Cats Eyes with model 6075AB, designed for 75 psi.

To determine the possible causes of your steer tire shoulder wear, I went to the Technology and Maintenance Council's Recommended Practices. Their Wheel and Tire Study Group developed RP219C, Radial Tire Wear Conditions and Causes. The RP contains photos and drawings to help identify each condition. It lists causes and suggests corrective actions. Your wear pattern is from over-inflation, excessive speeds or light loads.

By lowering your tire pressures to 75 psi all around, you should be able to drive safely and more comfortably at your normal loads, and your tires will last longer. LL