2 300ds running veg oil
 

i have an 83 300d and an 85 300d. the 85 has 220k and the 83 has only 80k. the 85 runs really well with the wvo but the 83 will only run well with it when the weather warms--the difference is remarkable. im in ca so its never all that cold for very long, but on the same morning i can fill these cars up, they will both start easily, but the 85 charges uphill on the freeway and the 83 will jerk and buck. i have changed many filters on both but never the filter which is in the gas tank on either. once this last winter when the temp was about 30 the 83 just would not ever turn over and i had to have it towed to the mechanic who got it cleared out and ever since then ive made sure to never have too much wvo in the tank. has anyone out there any idea why the 85 takes the wvo all the time and the 83 only when its warmer?? thanks for any feedback

Just as speculation I would guess compression. Have you done a compression test on both vehicles? There are a number of factors that could cause this just my best guess on the information you provided.

yes i have done on the 85 and its uneven, i had a stuck valve which was repaired but the compression is uneven --two cylinders a little low--and the gas mileage on the 85 is not as good as the 83 which idles smooth as silk--thanks for the response

How about air leaking into the fuel system on the '83, more when it has to suck harder when the WVO is really cold, or when you're going uphill?

Are you maybe mixing WVO with diesel #2 to "never have too much wvo in the tank"? If so, please short circuit the standard path and go do the research on blending WVO + D#2 blending before you put anymore WVO in your tanks.