Fuelish Question
Q: In the October 2006 “Tech Talk” column, your response in the “Diesel Fuel For 2007” (page 20) letter answered some questions I had about diesel fuel. However, I have a question that was not answered. I thought the lower the sulfur content of the fuel, the less lubricity it would afford. Thus, do we need to use an additive to replace the lubricity lost in the ultra-low-sulfur diesel (ULSD) fuel? I am thinking we should be using an upper cylinder lubricant (such as Lucas products), especially with the ULSD fuel. What are your thoughts on this?
Bill Schmees, F155779
Broken Arrow, Oklahoma
A: You’re right “” up to a point. The sulfur does provide lubricity, as you’ve surmised. However, it has been mandated for some time by the EPA that ULSD be the only diesel fuel available after January 1, 2007. Both the engine manufacturers and fuel companies have been well aware of this and have taken steps to avoid problems. I’m assuming you’re speaking about pre-2007 engines on the lubricity issue, as 2007 model-year engines are designed specifically for ULSD fuel. The only engines that may have trouble are pre-1990-era engines. And the trouble won’t be lubricity, but with some internal seals in the fuel system. The seals may become brittle and not seal properly. You can find out whether your engine may have problems with ULSD fuel by contacting its manufacturer directly. Any manufacturer will be happy to help you.
Low RPM = High Mileage
Q: I own a 2004 Coach House Platinum. It’s built on a Ford E-450 chassis, equipped with a 7.2-liter diesel engine and a four-speed automatic transmission, and has a gross vehicle weight rating of 14,050 pounds. I also have a Gear Vendors Under/Overdrive auxiliary transmission. At 60 mph the engine turns 2,200 rpm in factory overdrive. When I engage the Gear Vendors overdrive (while driving on level highways with no wind), the tachometer reading drops to 1,700 rpm. The engine does not seem to be lugging, and I still have speed left in the throttle. Will this type of driving damage the transmission or the torque converter, or cause heating in these or any other components? The engine hits its peak torque at 1,800 rpm. If driving as I have described is not harmful, what would be the verdict if I slowed to 55 mph and dropped the rpm to 1,200 (all driving conditions remain the same)? The purpose I have in mind is to save fuel; however, I would not want to compromise the equipment. Do you feel it is necessary to add transmission temperature or engine oil temperature gauges to this coach?
John Coffey, F291017
Carlsbad, California
A: To answer your questions, I’ll address the second one first. While I don’t see a necessity to add the temperature gauges to your coach, if you’d feel more comfortable with the additional information they’d supply, your increased relaxation while driving might be worth the cost. But I don’t believe that you need them.
As to your first question, I can’t see any damage occurring to your engine by decreasing the rpm; however, I don’t see any increased economy either. An internal combustion engine works more efficiently at its peak torque rpm, which according to your message is 1,800 rpm. I suggest you perform 55-mph, 60-mph, and 65-mph driving tests along the same highway in the same weather conditions and check your mileage figures. That way you can discover what your optimum driving speed should be.
A Simple Dead Battery Solution
I had a dead battery on the second day of towing my 2005 Jeep Grand Cherokee, because, out of habit, I left the ignition switch in the second position (off, unlocked) as was necessary on our 1996 Grand Cherokee. I reread the owner’s manual for the 2005 Jeep and found that the 2005 ignition switch must be left in the first position (the switch is “off” in the first position and is “acc” in the second position). The key must be left in the “off” position, because the steering column locks automatically when the key is removed. I use a dummy key (without the smart chip) to prevent theft. No more dead batteries, plus no extra wires or extra accessories needed.
Joe Brown, F269606
Newark, Delaware
Thank you for sharing this information.