Here is my post from another thread.
Original Quote:
Originally Posted by KevinGary View Post
I wanted to report back on my experience with Exxon Synergy Diesel. At the outset, let me say that I know that this is not a scientific analysis and that it is one person's experience.
I have 89K miles on my 3.0 A6 TDI. Almost all of my miles are commuting miles in the NYC metro area. I have hand calculated the mileage of every tank since new and have input it into an excel spread sheet. (yes I have OCD!). After 89k miles my overall MPG is 28.6563. During those 89K miles I used BP and Shell fuel exclusively. So I have a pretty good baseline for comparison.
In recent months I noticed a decline in my MPG and decided to give Exxon Synergy a try. I have now driven 1,136 miles on it and have averaged 29.2783 MPG, i.e. an improvement of .622 mpg, or an improvement of slightly better than 2% when compared to my lifetime MPG. This is about the same as Exxon claims. These last 1,136 miles were typical commuting miles for me. No extended highway trips.
Of course that it is comparing it to my lifetime mileage. However, remember that I told you that I had observed a drop off on MPG and that is why I tried Exxon Synergy. In fact, for the 6,619 miles before the switch my MPG had dropped to 27.272. The drop off started last August and when it happened I tried various fuel additives to no avail. By late September I stopped with the fuel additives and decided that the car was just getting older. So by the time I tried Exxon Synergy I had driven over 5,000 miles since adding any of the additives. Comparing the Exxon Synergy to the entire "dropped period" the mileage was 2.006 MPG better, ie 7.3% better.
Of course part of the entire "drop period" included the warmer months and the impact of the fuel additives. So I also looked at my MPG for the 1,150 miles before the switch. This roughly lined up with the same number of miles that I had driven with Exxon Synergy (1,136) and all of the miles were winter miles (January-March). During this period I averaged just 25.727 MPG on BP and Shell. When comparing that MPG to the 29.2783 MPG I got with Exxon Synergy, there was an improvement of 3.551 MPG, or 13.798%.
Based on my experience it seems that Exxon Synergy does a better job of cleaning the fuel system than the additives I tried (Stanadyne, Power Service, Liqui Molly and XPD) or the fuel offered by Shel and BP. It also seems to improve the MPG by .6 MPG in my car, or about 2% when compared to the lifetime MPG.
I know that this is not a scientific analysis, but I thought I would report my observations.
I have now used the new Exxon fuel exclusively for the last 4,276 miles and have averaged a hand calculated 30.16 mpg.
Updated Response:
I have refined my "baseline comparison number" because I could not believe the improvement. My baseline number no longer includes the car's first 14,965 miles, which I removed because it was the car's break-in period where it averaged 26.28 mpg. I also removed the mpg that I experienced from 77,891 to 87,473 because this was the period where my mpg dropped to 27.38 that caused me to try the Exxon fuel to correct whatever was going on. After removing these two periods, I am left with the 62,925 miles between 14,965 and 77,890, when the car averaged 29.49 mpg. I think this provides a fairer "baseline".
Against this revised "baseline" the Exxon fuel provided a 2.3% improvement, which is more in line with Exxon's claims. But what remains amazing to me is that the Exxon fuel seems to have cleaned out whatever caused my mpg to drop to 27.28 mpg for the 9,546 miles between 77,891 and 87,437. During that period I tried Stanadyne, Power Service, Liqui Molly and XPD trying to clean out whatever caused my mpg drop, and none of them helped.
So, while still not a scientific analysis, the fuel does seem to deliver the claimed mpg improvements and provide an effective "detergent".