Anyone got a good test method for sugar in the diesel lube oil? Smart answers about tasting it will be frowned upon..cause we aleady tried that!!!

Seriously, we currently try gentle heating on a watchglass and look for bubbling and caromelization, and a filtration since sugar shouldn't be so soluble unless it has already been cooked...

Any other ideas?

Talk to a lab. You might be just a simple (and cheap) phone call away from solution.

How about optical activity?
Mix oil with water - sugar extracts into water along with other polar additives - measure optical activity of water solution with polarimeter. below paragraph I pulled off Internet states sugar activity can be measured in water as well as gellatin -

Methods/Materials
a simple polarimeter with a light bulb, color filters, polarizing filters, and a sample cell. I prepared 100 - 200mm long columns of water solutions of sugars (sucrose, fructose, dextrose, and lactose),artificial sweeteners (aspartame, sucralose, and saccharin), or food products (sodas, syrup, wines, and jello). I measured the optical rotation of the sugars in solution by rotating the analyzer in the polarimeter until no light was transmitted.
Results
I found that the optical activity of sugars and artificial sweeteners can be measured and that the wavelength of the light, the solution concentration, and the liquid column height all change the amount of optical rotation. I also found that artificial sweeteners had much stronger optical activity than sugars.
Finally, I discovered that sugars in gelatins behave like sugars in water and that the optical activity of dextrose can change with time.
Conclusions/Discussion
All the common sugars and artificial sweeteners are optically active, while the artificial sweeteners had much stronger optical activity than sugars. These results mean that polarimetry is a useful way of
measuring the content of sugars or artificial sweeteners in beverages and food products.