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Oil Consumption Mystery

Originally Published in MotorHome Magazine

We recently ran into a problem with our motorhome that we can’t figure out. We own a 2007 Newmar Dutchstar powered by a 400-hp Cummins ISL turbo­diesel engine. It has about 36,000 miles on it. During our last trip, we suddenly began to go through a considerable amount of oil. Eventually, we discovered that we were losing about 1 gallon of oil about every 300 miles. I did not notice any loss of power.

I kept an eye on the oil pressure gauge and the temperature gauge and neither indicated there was a problem. I contacted Cummins and was told that as long as the oil pressure stayed within guidelines it would be safe to drive home. The pressure gauge was showing me running between 50 and 55 pounds of oil pressure and 20 to 25 at idle, which is well within guidelines. However, just to be safe, we stopped in Omaha, Neb., and again in Cheyenne, Wyo., to have two certified Cummins shops look at it. After three days, neither of these repair shops were able to locate anything wrong with the engine.

However, oil continued to disappear. Eventually, we replaced about 14 gallons of oil in about 3,000 miles. There is no indication of a leak anywhere. There are no drops of oil under the engine after stopping overnight, no spray of oil on our dinghy car, no spray or oil in or around the engine compartment and no oil dripping from the exhaust. Also, there is no evidence of burning oil such as blue smoke from the exhaust. The exhaust pipe shows black soot, but it is not excessively oily.

When we arrived home, we took the coach to a local Cummins dealer and told them what had happened. We left the motorhome there for more than four months so they could diagnose the problem. They finally gave it back and told us they had run out of ideas as to what the problem might be. They checked the turbo, the cooling system and everything else they could think of and could not explain where the oil is going. They, too, were unable to find any leaks. They also cut open the oil filter and were unable to find any indications of problems such as metal fragments. We have now changed the oil and filter twice in the last 1,000 miles without it helping. One suggestion was to start using heavier weight oil.
Russ Whitcomb | Helena, Mont.

These engines run well in most conditions using 15W40 diesel oil, and going to slightly heavier oil, such as 20W50, won’t make an appreciable difference in your situation. Make sure you are not overfilling the engine oil.
Due to their high compression ratios, diesel engines can burn a lot of oil before it starts to show in the exhaust. There are several things that can cause high oil consumption similar to what you report. A blocked crankcase ventilation system can cause a sudden rise in oil use. A cracked oil ring could also cause high oil consumption. It should cause blue smoke, but it might not. One easy way I check for internal blow-by and cylinder-sealing problems is by removing the oil filler cap while the engine idles. Compare the amount of fumes coming out to a known-good engine. If it is blowing out a lot of fumes, have a cylinder leak-down test performed to locate the problem.
The most likely cause is a failed oil seal in the turbocharger. Heat and age get to them, and cause engine oil to migrate into the air stream going into the engine, where combustion burns it up. I know you mentioned that they “checked” the turbo, but how did they check it? You can’t tell by looking at it, and boost will be normal. A faulty turbo oil seal is consistent with all of the other factors you provided, which indicate an otherwise healthy engine. Turbo seals are likely to go bad if you run the engine hard, such as up a grade, and then shut it off without letting it idle to cool down for several minutes. It only takes one time.

Towing Mileage

We own a 2011 Winnebago Adventurer with Ford gasoline V-10 engine. For the past three years I have been towing my 2004 Jeep Grand Cherokee across the country. I am erratic in that sometimes I use cruise control and go a reasonable 60 to 65 mph. At other times, I get impatient and go at higher speeds and lose mileage. On average, I am between 6.5 to 7.5 mpg. Now I want to replace my Grand Cherokee with a new one. However, the 2014 version of the same vehicle weighs 1,000 pounds more. Though this weight (4,800 pounds) is still within the safety limits for my motor­home, I am wondering how the extra weight will affect my mileage.
Bill Rostron | Middle Island, N.Y.

The fuel economy you report is within the typical range for this kind of use. Best fuel economy will probably occur at a slightly lower speed, between 55 and 60 mph. Going 70-plus (or into a strong headwind at lower speeds) can easily result in a 20 percent penalty. Accelerating that extra weight and hauling it up hills requires more fuel than cruising on the flats. There’s no accurate way to estimate the difference to expect, because rolling resistance, wind resistance, etc., vary among models. However, you can get a rough idea by calculating the difference in weight. For instance, if you add 5 percent additional weight, expect up to a 5 percent loss in mileage. The loss of fuel economy will also be greater in hilly country than on flat roads at steady speeds. Make sure the tires are properly inflated, as this can make a significant difference too.

Contaminated Diesel Fuel

Can diesel fuel become contaminated to the point that it would cause major fuel system components to fail? I was unaware of such a thing, but I’ve learned it happens after consulting with others, and apparently this could have been why our coach died on a busy highway shortly after filling up at a fuel station.
To replace the pump, my bill was $3,150 ($2,200 for the pump, plus labor) and I am trying to ascertain whether the root cause was the fuel itself or the failure of the 12-year-old fuel pump. I have been driving motorhomes since 1973 and a diesel pusher for the past 10 years. Is fuel contamination myth or truth? If truth, what recourse, if any, can be taken?
Roger Haddock | Geneva, Ohio

Diesel fuel is prone to contamination from water and other substances picked up from storage tanks, transport and the vehicle tank. Temperature changes often result in water vapor in the air above the fuel condensing into water and settling to the bottom of the tank. Microbes often live in this combination of fuel and moisture. That is why diesels have such large fuel filters and often have water separators. In fact, one of the most common causes of on-road breakdowns of diesel vehicles is due to fuel contamination and clogged filters.
It’s very difficult to prove the source of contamination, as it’s often a gradual buildup. If your engine quit shortly after refueling, and the tank was found to contain a large amount of water or other contamination, you would have a stronger case against the fuel seller. The tank should have been inspected and cleaned out if any contamination was found. Also, the injection pump should have been disassembled and inspected by a diesel specialist to determine the cause of failure (sudden, due to contamination, or long-term due to wear and tear). Armed with this information, you would have had a better chance of recovering your costs from the seller, if, in fact, the station was the source of contamination. This could have been done with a direct request, or if that was refused, through small claims court.

Shattered Shower Door

Last spring, my wife and I were enjoying the peace and quiet of a Wisconsin campground in our 2004 Fleetwood Southwind when we heard a crash. We went to the rear of our motorhome and saw that one of the glass shower doors had shattered into a million pieces. The shower door hung in a track and was under no stress. We were parked on a level asphalt site and had been parked for several hours. We’ve had the motorhome since it was new. The dealer from whom we purchased it new was as baffled as we were. After the experience, we decided to replace the door with an accordion pleated shower door from Camping World. What happened to cause this?
Don Wiberg | Frankfort, Ill.

These doors are made from tempered glass, similar to what is used in many automotive side windows. They are designed to break into small pieces, which aren’t as dangerous as long shards from non-safety glass. However, they can still cut you. Tempered glass can be broken fairly easily. What is likely to have happened is that there was a small flaw in the glass, either from manufacturing, installation, or use. Then, on that day, when the glass warmed up, thermal stresses caused it to fail catastrophically.

Refrigerator Tip

How well your RV refrigerator cools is a function of how quickly and effectively the cooling unit can exchange and dissipate the heat. On a hot summer day, especially if the sun is hitting the refrigerator side of the vehicle when the cooling is most needed, the unit often has a difficult time getting rid of the heat in the coils. Some people open the outside refrigerator access doors to let in more cooling air. I found a better and more efficient way was to place a muffin fan inside the cooling coils pointing upward. Using plastic ties, I secured a fan a few inches off the bottom and oriented the fan so that the air passes up through the center of the coils. There are usually plenty of places to wire the AC or DC fan in the compartment. I installed a switch so that I can turn the fan off when it isn’t needed. I found the refrigerator’s efficiency increased to the point I had to turn the temperature setting up.
Harold Borland | Cottonwood, CAlif.

Thanks for writing and sharing your experience, Harold. Camping World and other RV stores offer several fan kits, including one that’s solar powered, which ensures it can’t run down the battery.

Windshield Popping Out

I have a 2005 Santiam Class A motor­home built by Beaver. The windshield on the passenger side has started to fall out of the coach on three occasions. Twice, this happened while on the road. I went to a windshield repair shop and had it “fixed.” The first time, they removed the glass, cleaned it and the gasket, and reinstalled it. About 50 miles down the road, it started to fall out again, coming loose in the lower right corner and beginning to slide out. Lots of duct tape held it in place until I got home. The third time, the coach was sitting in the driveway for two months when I noticed it was beginning to come out again. I have searched the Internet to find a solution with no luck. Help!
John Weston | Hesperia, Calif.

The windshield opening is probably just a little too large. This allows the glass to pop out when the coach flexes as it goes over bumps. As you probably know, Beaver is no longer in business and Allied Recreation Group has taken over. You may be able to obtain dimensions and perhaps a drawing of the windshield opening from the company by calling 877-466-6226.
You can take it to the Beaver/Monaco facility in Coburg, Ore., to have the opening checked and, if necessary, modified. I checked with a factory tech rep and was told the shop will offer this service on your coach (for a fee). There should be between 3/8 and ½-inch of clearance to the body opening edge, evenly around the glass. The factory uses a urethane glue on the glass and the body where they contact the rubber seal. The tech rep also recommend that the coach sit for one to two days to allow the glue to set fully. Alternatively, a good RV shop that does collision repairs should be able to get the windshield to fit properly by building up the opening, if necessary.

Intermittent Power Loss

We have a 2001 Newmar Dutch Star with a 3126B Cat engine and a Power EZ module (ECAT1000), which is set to increase horsepower from 300 to 330. I installed a boost gauge to help troubleshoot a problem where the engine will not increase power. It started last year on a trip and happened a half-dozen times. I didn’t have a boost gauge installed then.
Recently, we were on a trip and had no problem at first (boost pressure went from about 10 to 35 psi depending on load). Then, as I was in traffic going about 40 mph, I stepped on the accelerator and there was no change in boost pressure. I floored the pedal and dropped a gear, but still no change in boost pressure. Finally, after about three minutes, the boost pressure went up to 35 and my speed increased.
There are no exhaust leaks, and the coach has new air and fuel filters. It seems that if the wastegate had stuck open, then the problem would be all the time. I know it’s hard to troubleshoot intermittent problems, but any suggestions would help.
Rodney Nelson | Eureka, Calif.

This aftermarket power module modifies fuel delivery and boost pressure. It was made by Edge Products (888-360-3343, www.edgeproducts.com). Unless you have an increase in fuel delivery, you won’t build more boost, even with the waste­gate closed. It’s likely that your engine isn’t responding because it isn’t getting enough fuel, not because the wastegate is stuck open. If the wastegate was stuck open, you would still get some engine response, although it would be weaker than usual. I recommend installing an exhaust gas temperature (EGT) gauge whenever the engine is modified with aftermarket parts. High EGT would indicate excessive fueling; low EGT would show that it wasn’t getting enough. It’s fairly easy to temporarily disconnect the aftermarket module. Try doing this, as it will eliminate or verify the unit as a source of the problem.

Power Awning Problems II

This is regarding “Power Awning Problems” in the March Coach & Powertrain. I had the same trouble and it turned out to be caused by crossed wires in the RT-11 connector at the wind sensor. The problem could occur at either end of the cable. The solution is simply switching the wires.
Richard McGregor | Elkton, Va.

Thanks for sharing your solution. It’s something you wouldn’t normally expect.




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