I have two 6.7 diesels.

How hot can I let the engine oil get?

I was told (by ford dealer mechanics) to not let it get to or past 240F.

Both my 6.7 diesels get close to 240F (I mean, I got both to 239F!!!) very easily when on a grade towing a 7200 lbs. gross weight toy hauler trailer.

I am very disappointed because I tow (going to the desert to ride dirt bikes from San Diego to Borrego Springs) together with a fried with a dodge and he cannot get his truck engine oil past 212F!

It seems to me the oil cooling is very inadequate on these 6.7 turbo diesels...

Opinions/experiences please!!!

 

I have pulled my 15K 5th wheel up 6% grades at 100 degrees outside temperature doing 55 MPH and my oil temp never got above 230. Definitely better then what you are experiencing.

 

1. This engine will not allow itself to melt. There are many sensors and software parameters built into the ECM and it simply will not let you push it too far.

2. Are you running stock or tuned?

3. You may want to consider driving those grades/mountians a little more conservatively.

4. You run 5W-40 oil?

5. Secondary coolant system full?

6. There have been problems with the fan clutch. Is your cooling fan coming on? I believe it comes on at 240° so I would think it's not an issue for the oil to get that hot.

 

Double the weight that you are towing and head up the mountains in the Summer and you still won't see it go much higher. The oil cooling system works well, but don't expect it to keep things under 210 all the time. I'm guessing that at 239 your fan clutch did not engage yet. If memory serves me, mine kicks in around 243 and I've never seen over 245. I have to work it pretty hard to get things that high and there isn't a climb on the East Coast long enough to for me to test it any further.

The worst I have seen is about a 6 mile climb at 6-7%. Oil temps seem to peak at 3-4 miles into the climb and don't get any worse before the summit. The systems on these trucks seem to have precise control of everything. With two different temperature range thermostats in each cooling system, it works differently than we are used to. Everything reaches a higher temperature than we are used to prior to both thermostats being wide open. It seems to reach what I would call maximum temperatures rather quickly, but is very capable of keeping them from escalating further.

To answer your question on max oil temp, it depends on the oil that you are using, but 240F for extended periods is a good rule of thumb. I wouldn't get excited over peak temps of anything less than 250F for short runs.

 

Maybe u should sell them and buy a couple dodges if your so disappointed

 

 

This is one reason I prefer to use synthetic oil. At 240 degrees, conventional oils will just begin to break down whereas full synthetics can get to about 400 degrees without concern. I've raced (well, not exactly racing, but sort feels that way when I blow by the semis) up long steep grades in the heat of summer with a heavy trailer and have seen the engine oil get to 240 degrees. It does seem to stop there though no matter how hard I push it.

 

I'd check to make sure you are running the right oil for the towing and heat. 15/40Wt is what I run.

 

Thanks for all the answers guys!

The only reasons I am concerned are:

1-I asked how hot I could have it (before it became an issue) and the dealer told me not to let it get to 240F.

2-Both mt 6.7s do it the same way... (one is a dually 4x2 and the other is a single 4x4)
*Driving VERY conservatively (trying not to heat it up)
*During mild days (70 to 75F ambient temp)
*On 6% grades
*Pulling a light trailer (7200lbs gross)
*They get hot quick. The jump from 200F oil temp to 235+ only takes a few corners....

As for the engine oil itself, I have a service plan on both. So it is whatever the dealer puts in it. I was assuming it was good synthetic stuff! It seems I am very wrong....

 

Pulling my 5er, in the mountains of Tenn, NC and into SC, I consistently see oil temp of 240 up to 244. Fan has never kicked on. Had fan checked and it is working properly according to tech. Tech said the high temp was normal for this engine and not to worry. My old 5er weighed around 14.5k, new is over 15k. I just switched to full synthetic and will see if any different on temp once summer shows up.

 

Mine will hit the 242 - 243° on long hard pulls with 13,000lbs of trailer behind me on 100° days. I've never seen it go over that.

The 6.7L engine uses the oil to help cool the engine. It squirts a jet of oil at the bottom of each piston on each stroke. This oil helps carry off the heat, which the oil takes to the oil cooler and passes on to the coolant.

When these trucks first came out, We had a Ford engineer online answering questions. We asked him about that, He said that the Ford engineers had designed the engine for those temps and the oil would stand up to it. It was just part of the over all big cooling picture.

I think your dealer is just a couple of degrees too cool. Think of 242°-244° as your max and you will be fine.

 

I hate when dealers just pass out random information without actually knowing the manufacturer's stance on the issue. EOT is one of the parameters that triggers the fan clutch to fully engage. If 240 is indeed the maximum temperature that Ford wants the oil to reach, why wouldn't they program the fan clutch to kick in at 235 or less to prevent it from ever reaching max temp?

The general consensus I have seen on the forums is that the fan clutch does not engage until well over 240. It seems a little pointless to try to cool things down after you have reached the maximum allowable temperature. Lets take Ford totally out of the equation and look at this rationally. No matter what the engine manufacturer says, if you are using a different oil than what their opinion is based on, their findings are no longer valid. If you are using an inferior oil, what they tell you could be 10-15* higher than where your oil is safe or if you are using a premium pure synthetic, you could go much higher and still be safe. Oil temperature thresholds are more about protecting the life of the oil rather than the engine itself. Coolant temp is more representative of engine damage thresholds. Because this engine uses the oil for cooling purposes as well, EOT will be higher than what you are used to. If the coolant temp is pushing up over 230, the oil is always going to be at least 10* hotter than the coolant as the system is not 100% efficient to keep EOT the same as ECT.

As for the dealer service plan, dealers make most of their money on service work and very little on the sale of the vehicle. The best way to make money is to cut corners. Many dealers that offer oil changes for life or service plans use bulk oil to save money. It is possible that your dealer isn't even using Motorcraft oil. The best advice is to find out what they use and look up what the oil manufacturer says.

 

Well said 720.

Also, with this engine, I don't think there's any chance of it to allow itself to keep running if the temp reaches the high limit. I can't prove it but based on all the other ways the engine protects itself, there must be a reduced power/shutdown in the ECM.

 

I have seen as high as 240, pulling 19K. No issues.

 

I don't think that's accurate Tuevo. I'm having a tough time finding a lot on the CJ-4 spec, but the previous gasoline engine oil spec required far more than 240° from oil. In fact the testing for API SM oil tests it in an engine at 302° EOT for 100 hours straight, only stopping every 20 hours to check the oil level. If conventional oil broke down at 240° there's no chance a conventional API SM oil could exist, yet there are many.

SwRI: Sequence IIIG test for gasoline engines, API SM, ILSAC GF-4

For API CJ-4 oils I can't find an endurance test at high temperatures like this, but there is a minimum viscosity at 302° F.

http://www.swri.org/4org/d08/chemtests/HiTempShear.pdf

I'm no oil chemist, but I'd venture to say that there is no chance that conventional oil breaks down around 240° if the standards for both gas and diesel oils require it to perform at 302°.



It matters not what the name says on the bottle or barrel. As long as it's a CJ-4 certified oil of the correct weight it meets the spec.