I recently switched to the Shell synthetic oil , and while I know its normal for my truck to put out a little white smoke while its cold, I am now getting more then a little in just accelerating up to the 50 MPH range. Could this be the lower viscosity of the synthetic ? It seems to go away after it gets warm, and I have not used a measurable amount of oil in the 400 miles since I changed it. My truck is a 95 standard shift 3/4 CTD.

 

how many miles on the engine? maybe too many to go synthetic? just a thought.

 

170K miles, the dino oil was 15-40, the synthetic is 5-40.

 

I personally wouldn't change over to synthetic with over 100k, you're only asking for problems.

 

Hello...

I really don't think the cold-start white smoke which clears after warm-up has anything to do with your choice of lube oil... White smoke when cold is definitely a fuel control issue, i.e. a portion of the injection charge is unburned because the cold cylinder does not offer complete compression ignition until operating temp. is reached... Smoke associated with lube oil control is blue in color...

White smoke at cold start 'til warm is considered normal for pre-electronic engines with the old mechanical fuel systems... The mechanical fuel system is set to optimize delivery at operating temp, and as noted above the injection charge doesn't compensate for cold temp. ...

Electronic engines DO offer cold smoke control, however... It is only with the contemporary ELECTRONIC engines that offer PRECISE injection metering for the entire temp. range. This is done by the ECM, based on temp sensor info (various engines have up to 3 temp sensors (ambient inlet air, oil, coolant), and when cold, the ECM is informed and tells (controls) the electronic injectors to limit the fuel, thus limiting cold white smoke.

Bottom line... Knowing the above now,

1.) Check for codes / particularly related to a possible bad temp sensor... possible the ECM is not getting the right info...

2.) Possible worn injectors... Have a tech run them on a test fixture...

 

No ECM on a mechanical 12 valve. The 12 valve temp sensor is only used for the grid heaters.

 

It seems all the discussion has cured the problem, I have not noticed it the last few cool mornings here in Idaho

 

Suggestion.

Synthetic oil is a better 'cleaner' then dino oil. Running synthetic after that many miles with dino oil is bound to loosen up and clean the internals of the engine. Might not hurt to change the synthetic oil and filter a time or two at frequent intervals to make sure you catch and get rid of all that loosened 'dirt'.