GC for Fuel Dilution - Accuracy

Messages
3,931
Location
Decatur AL USA
Thread starter
3.5EB Runs between 900 - 9500 mi GC shows Fuel Dilution between 1.5 -4.7% with no correlation with mileage. How is it possible to hit near 5% at less than a 1,000 mi and be as low as 1.5% at nearly 10,000 mi without any appreciable change in level on the oil stick. Shouldn't a 5% gain in less than a 1,000 mi result in a half quart rise in level and if it cooks off before the end of a 10,000 mi OCI shouldn't the level drop? It's got me doubting GC is more accurate than a Blackstone guess.
 
Messages
820
Location
Upper midwest
I can gain 3/8qt in the summer with my Hyundai 1.6T in the first 500 miles. I am at 5+%-7% during the Minnesota winters from Polaris Labs advanced test, the one you have to force them to do. I can gain a qt as I pull some out after 1/2 gain. I don't have any wear issues. I check UOA from time to time, but I am long pass any worrying about fuel dilution, other then keeping an eye on it.
 
Messages
180
Location
Maryland
First off, GC in this context stands for Gas Chromatography (an analysis process) which involves using an instrument known as a Gas Chromatograph. To answer Gene K's question, a 5% increase in volume in oil as a result of fuel dilution might not make much of an appreciable rise in the level on the oil dipstick. For an engine with a 5 quart requirement, a 5% fuel dilution will only add 8 ounces (1/4 quart) to a system already containing 160 ounces. As to why the fuel dilution drops from ~5% at 1000 miles to as low as 1.5% at 10,000 miles, I would explain it in terms of the engine wasn't driven enough to get the oil hot enough in the first 1000 miles to evaporate the gasoline out of the oil, whereas as time went on, the engine was driven enough to get the oil hot enough in order to evaporate the the gasoline out of the oil by the time the 10000 mile mark was hit.
 
Messages
628
Location
LA (Lower Alabama)
Originally Posted by Gene K
... How is it possible to hit near 5% at less than a 1,000 mi and be as low as 1.5% at nearly 10,000 mi without any appreciable change in level on the oil stick. ...
A dipstick is not a precision-grade measuring device.
 
Messages
8,723
Location
Houston, TX
Originally Posted by chemman
To answer Gene K's question, a 5% increase in volume in oil as a result of fuel dilution might not make much of an appreciable rise in the level on the oil dipstick. For an engine with a 5 quart requirement, a 5% fuel dilution will only add 8 ounces (1/4 quart) to a system already containing 160 ounces.
^^ this ^^
 
Messages
53
Location
USA
To answer this directly, we do not have a GC but the lab we use for GC said when trying to determine fuel dilution by GC they would report in 5% increments. It is difficult to be precise.
Originally Posted by Gene K
It's got me doubting GC is more accurate than a Blackstone guess.
 
Messages
13,343
Location
1/2 hr N.E. of Detroit
Originally Posted by super20dan
ENOUGH WITH THE ACRONAMS IN THIS SITE! people to lazy to type!
....Enough with the acronyms on this site. .................. People too lazy to type! approved I agree with you Dan. thumbsup
 
Messages
3,931
Location
Decatur AL USA
Thread starter
Originally Posted by Oliveoil2
Green Castrol made in Germany.
You can still get Green Castrol? Besides I think the Germans Imported it. I heard it was made by Leprechauns in Ireland. The gold was domestic German production.
 
Last edited:
Messages
8,723
Location
Houston, TX
Originally Posted by Gene K
It's got me doubting GC is more accurate than a Blackstone guess.
Why? Labs like Polaris using a GC for fuel dilution measurements do not have issues with accuracy. Unless something has changed, Blackstone uses an entirely different method that is very subjective and requires watching a flame at a very specific time.
 
Messages
180
Location
Maryland
Analysis by gas chromatography can be extremely accurate provided the laboratory doing the analysis runs the appropriate standards and calibrates their instruments on a periodic basis. Gas chromatography is routinely used to analyze samples for components present in the parts per million and parts per billion range.
 
Messages
2,275
Location
Southwest Virginia
Analysis by gas chromatography can be extremely accurate provided the laboratory doing the analysis runs the appropriate standards and calibrates their instruments on a periodic basis. Gas chromatography is routinely used to analyze samples for components present in the parts per million and parts per billion range.
And is also great to identifying and quantifying base oils (with experience).
 
Top