For any of you who are interested in the fuel testing approach with a hydrometer, I did a little looking online, and found the following.

- Need an API hydrometer that measures from 29-41 degrees.
- These are available with or without built-in temperature indication (although temperature affects density and specific gravity in general, it does so much more for gaseous compounds than for liquids or solids... therefore, the temperature option is not necessarily critical)
- I have found these units at multiple lab supply centers, and they range from $10-$42 each, depending on size, brand, and marketing strategies
- they are available in 7-1/2 inch, 13 inch, and 15 inch models
- there is even someone selling one on eBay (auction closes tomorrow)

Here are a few links:
http://www.novatech-usa.com/s.nl/it.A/id.3061/.f ($30.50, w/ temp)
http://www.wlwalker.com/sites/WLW/sp...groupid=HYD7CF ($19.17, w/ temp)
http://www.wlwalker.com/sites/WLW/sp...bgroupid=HYDIN ($28.95, w/ temp)
http://vwrlabshop.com/product.asp_Q_pn_E_0009295 ($42.63, w/ temp)

and finally,

http://www.wlwalker.com/sites/WLW/sp...bgroupid=HYDPF ($10.39, no temp)

 

Oh...

...and the API standard for diesel is, I believe 38-39 degrees API (not to be confused with temperature degrees).

 

My hydrometer cost $75. I'll have to look at the range, its marked, green for good range, yellow for acceptable, etc. Here is an item number on ebay 220056033461 for a hydrometer. Range is 29 to 41. Here is a link to a good article from the Engine Manufacture's Association http://tdiclub.com/articles/Diesel_Fuel_Guidlines/

API specific gravity recommendation from 39 to 43, you can read how the SG effects combustion and power. I'm suprised no one on here talks about testing fuel. A hydrometer is not that expensive and its one of the best ways we can be sure to put good fuel in our trucks. I'm gonna start a thread and see what people say.

 

great footwork on the hydrometer info F250-Newbie.