Well, there were a number of things that Mercedes did with this car that were marginal - the cooling system being ine of them. Oil is supposed to (from what I understand) have more BTUs than diesel. It may also burn at a higher temperature than diesel whether it has more BTUs or not. If the cooling system is marginal, it would show up. When I started the thread, I wasn't sure. Now that I've done some more work on the car, I know for sure that there is more heat put into the engine when running on oil. The only thing I don't know is "why."
WMO burns hotter than diesel?
- Thread starter paramax55
- Start date
Josh Carmack
Full Access Member
Oil depending on the source has anywhere from 5 to 15 percent more BTU's in a gallon. I see a difference running it, not a huge difference, but I do see it.
OK. I'm REALLY starting to get tired of chasing gremlins in this car... it's a giant headache. I'm going to have to hold off for a day or two. It looks like I have a bad injection pump. But I'll start another thread for that.
TDI
Full Access Member
WMO contains anywhere from 150,000 to 180,000 BTU's of energy per gallon. # 2 home heating oil ( diesel fuel) contains about 138,000 BTU's per gallon. I am not exactly sure how to calculate the temperature increase but a back of the envelope calculation your 20% increase is staring me in the face.
More energy per gallon means more heat per gallon. That is why when I do conversions in buildings from #6 heating oil to # 2 heating oil the fuel consumption goes UP because 6 oil has more BTU's.
More energy per gallon means more heat per gallon. That is why when I do conversions in buildings from #6 heating oil to # 2 heating oil the fuel consumption goes UP because 6 oil has more BTU's.
Definently will be awhile till i can get any solid egt numbers for wmo. Winters around the corner here so im already adding no1 to fuel. No1 by itself has altered the egts to be a bit hotter with no modification to my wmo mix. Im seeing around 30F degree difference cruising at 75mph and about 120F higher peak with hard accelerations with 50/50 no1 & no2. EGT are all over so it makes it hard to see exact numbers. Ill be backing out of the wmo in a few months but due to the heat increase with no1 it may toss the numbers so im not expecting anything accurate till late spring.
Josh Carmack
Full Access Member
I'm glad you posted here and reminded me what I have meant to post several times. I replaced the radiator cap with a new one and have not run even remotely hot ever since. I have pushed the gauge slightly above 100 when in tightly packed neighborhoods and giving it all the throttle I can, but not something it didn't recover from as soon as I had the chance to get it above 40 mph for a few seconds. The electric fan doesn't even come on nearly as often.
I got to noticing it was ******* water on the ground when it wasn't even running hot so I replaced the cap. 4.99 has sped my return times up on the rt. by over an hour, and allowed me to relax a LOT. I no longer look over at the gauge every 30 seconds. I was literally glancing over at the gauge every box I stopped at so I would know ho hard I could take off to the next one. Now I just go. Funny how the cap was the problem, even though it doesn't have the original cooling fan in place.
Good thing about the missing fan is I am able to ford water past the door seals no problem now. Good thing too, because I live in a flood zone that normally floods every year.
I got to noticing it was ******* water on the ground when it wasn't even running hot so I replaced the cap. 4.99 has sped my return times up on the rt. by over an hour, and allowed me to relax a LOT. I no longer look over at the gauge every 30 seconds. I was literally glancing over at the gauge every box I stopped at so I would know ho hard I could take off to the next one. Now I just go. Funny how the cap was the problem, even though it doesn't have the original cooling fan in place.
Good thing about the missing fan is I am able to ford water past the door seals no problem now. Good thing too, because I live in a flood zone that normally floods every year.
I'll have to try the cap, but there's another issue. I finally took out the infrared thermometer and started poking around. The radiator and it's hoses stay nice and cool. The radiator will run around 140F to 160F and the thermostat housing will run around 170F - on the radiator side of the thermostat, but on the engine side of the thermostat it will be 220. I've flushed the cooling system, gutted the thermostat, replaced the water pump, and still the same thing. The heat exchanger was already in the car when I bought it and I'm suspecting it's too "free-flowing." There may be too much water bypassing the radiator. I'm going to buy a valve and try shutting it down some.
About the heat of oil... I understand that oil should have more BTUs, but I don't get any more power with WMO. My interstate speeds are almost exactly the same with either fuel. More BTUs SHOULD mean more power.
About the heat of oil... I understand that oil should have more BTUs, but I don't get any more power with WMO. My interstate speeds are almost exactly the same with either fuel. More BTUs SHOULD mean more power.
Blownoiler
Registered User
That sounds like the most logical place to look.
The burn rate of the oil probably has a bearing here, a slower burn generally leads to higher engine temps, just as retarding the injection timing can lead to overheating. Is the pump able to draw enough of the thicker oil to operate correctly?
Interesting you should mention about the timing... I was thinking the same thing a while back and I was going to try advancing the pump a couple of degrees but I went on vacation and forgot about it.
As far as having trouble with the oil... I'm mixing 20% RUG, it gets heated before it goes into the engine, and the engine runs smoother on oil than on #2, so I'm not suspecting any issues there.
20% RUG seems to have solved my coking problem and, if I remember correctly, 50% #2 didn't overheat. I might try adding some #2 to my formula and see what that does.
As far as having trouble with the oil... I'm mixing 20% RUG, it gets heated before it goes into the engine, and the engine runs smoother on oil than on #2, so I'm not suspecting any issues there.
20% RUG seems to have solved my coking problem and, if I remember correctly, 50% #2 didn't overheat. I might try adding some #2 to my formula and see what that does.
Blownoiler
Registered User
I add 5-10% rug to my veg oil in the winter, this gives more power and helps the thicker oil to flow , yet engine temps rise as rug is blended into the mix. I won't go over 10% rug because I'm concerned about why the engine temp rises. As far as I understand the composition of rug, the lighter fractions burn almost immediately, creating higher peak temps in the chamber, while some of the heavier fractions don't evaporate and burn until much later in the cycle (if at all)...hence the blue smoke emitted when too much rug is used in the mix. My solution is to mix in diesel instead of rug, which results in a lot less blue smoke when taking off on a cold engine.
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I think my temps actually went down about 10F when I started adding RUG and I know I get a lot less coking at 20% than I had at 10%. When I was just adding 50% #2, I don't think I had the overheating issue, but my prechambers coked so bad (never ran straight #2 at that time) that I was down one cylinder and I had trouble getting the glow plugs out. Straight #2 (Shell specifically) will clear it up within 30 miles if I get coked up too bad.
I also think veggie oil is a different ball game than WMO. I've been WMO from the start since it practically falls into my lap.
I added a valve to the heat exchanger line and shut it almost all the way down. It seems to have helped with the overheating issue. I'm not ready to say it's solved (I haven't driven on a hot afternoon yet) but it's definitely better.
I also think veggie oil is a different ball game than WMO. I've been WMO from the start since it practically falls into my lap.
I added a valve to the heat exchanger line and shut it almost all the way down. It seems to have helped with the overheating issue. I'm not ready to say it's solved (I haven't driven on a hot afternoon yet) but it's definitely better.
Josh Carmack
Full Access Member
It's funny how a cap solved mine, only thing I can figure is without the cap the coolant can't absorb as much heat before it flashes to boil, so it was flashing before it could get all the heat moved to the radiator, thus leaving it in the block, and then of course boiling off and needing to be refilled in a couple days.
Blownoiler
Registered User
Wow, that's a lot of build-up, is the engine down on compression at all? Are you driving at low revs mostly or do you run up to high revs frequently?, a good run in the higher rev range helps to clean out the ring pack, I think that the g forces generated actually throw a lot of the gummy crap off the piston ring area, which usually results in better sealing/less blowby.
Thanks for the tip!
Yes, the 2 different oils don't seem to share many characteristics when using them as a fuel.
The temps. you gave earlier for the before and after thermostat reading might point to a lack of coolant flow, how old is the waterpump and has the system always ran with an inhibitor in the mix?...is your fanbelt a bit on the loose side?...just thinking out aloud!
I rev the *** out of this thing. There are shift indicators on the speedometer and they don't tell you to shift until it almost runs out of air. The shift points are 22, 32, and 60 MPH. Look back a couple of posts and you will see that I just put in a new water pump and the old one looked brand new. Apparently someone else tried to solve the same issue before me.
I've come to realize that most of this car's problems stem from the fact that it was designed by an autistic child at summer camp. There are a lot of stupid things designed into this car.
I've come to realize that most of this car's problems stem from the fact that it was designed by an autistic child at summer camp. There are a lot of stupid things designed into this car.
Blownoiler
Registered User
"Shift Indicators"!...I've never had a vehicle equipped with one, other than the sound of valvebounce echoing into the cabin
.
There's a challenge for you, persist until the problem is solved!
It seems that the designers have to give a vehicle a reasonable short lifespan to ensure that they sell more new cars in the near future.........fortunately my vehicle is 21 years old, and is built on a box tube chassis, so I'm hoping for a few more years use, also I'm trying to avoid those damn computerised engines that newer vehicles have!
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