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Loading...Four DEXRON VI automatic transmission fluids went head to head: the AC Delco fluid distributed by General Motors, the Super Tech store brand, a Mobil synthetic blend, and Red Line's D6 ATF. Each ran the same sequence — 200-gram samples held at roughly 410°F for two hours to measure evaporation loss, a pin-and-wheel lubricity test measuring wear-scar diameter, timed flow races at about 70°F and at -40°F using both fresh and heat-cycled fluid, a five-minute foam test, and a full independent lab oil analysis of every fluid.
Price and performance do not line up neatly here. The $9 store brand finished second overall, while the $13 synthetic blend lost 20.61 grams to evaporation — more than twice what either full synthetic under $10 gave up. The $23 fluid did sweep the testing, and the lab work explains why: roughly two and a half times the anti-wear additive content of the competition, and a detergent dispersant package above 300 parts per million.
Best Performance
First place in every category
Average Finish: 1
Purchased for: $23
Made In: USA
D6 ATF marketed for GM DEXRON VI applications as well as several other automatic and manual transmissions. It took first place in every category: 6.94 grams of evaporation loss, the smallest wear scar of the four, and 24.53 seconds on the -40°F flow course, with lab analysis showing roughly two and a half times the anti-wear additive content of the rest.
Red Line lost only 6.94 grams to evaporation, produced the smallest wear scar, and finished the -40°F flow course in 24.53 seconds against 30.16 for the next-quickest fluid.
Best Value
Second overall at about $9 a quart
Average Finish: 2.8
Purchased for: $9
Made In: USA
Full synthetic fluid rated for both DEXRON and MERCON applications, and the second-cheapest quart in the group. It finished second overall with an average finish of 2.8 and had the second-lowest evaporation loss at 8.34 grams, though its 8.44 mm wear scar was the widest of the four.
Super Tech finished second with an average finish of 2.8, had the second-lowest evaporation loss at 8.34 grams, and held up better than the AC Delco or the Mobil at -40°F after heat exposure.
Best Low Cost
8 mm wear scar for about $8
Purchased for: $8
Full synthetic DEXRON VI distributed by General Motors and marketed as backward compatible with earlier DEXRON automatic transmissions. It tied the Mobil for the smallest wear scar at 8 mm, but it was the slowest fluid at -40°F both before and after heat exposure, and it gave up the most room-temperature flow speed after the heat cycle at 7.7 percent.
AC Delco was the cheapest quart in the group and tied the Mobil for the smallest wear scar, roughly five percent narrower than the Super Tech's 8.44 mm.
| Name | Purchased for ($) | Average Finish | Link | Made In | |
|---|---|---|---|---|---|
| Red Line | $23.00 | 1 | Search on Amazon | USA | |
D6 ATF marketed for GM DEXRON VI applications as well as several other automatic and manual transmissions. It took first place in every category: 6.94 grams of evaporation loss, the smallest wear scar of the four, and 24.53 seconds on the -40°F flow course, with lab analysis showing roughly two and a half times the anti-wear additive content of the rest. | |||||
| Super Tech | $9.00 | 2.8 | Search on Amazon | USA | |
Full synthetic fluid rated for both DEXRON and MERCON applications, and the second-cheapest quart in the group. It finished second overall with an average finish of 2.8 and had the second-lowest evaporation loss at 8.34 grams, though its 8.44 mm wear scar was the widest of the four. | |||||
| AC Delco | $8.00 | Search on Amazon | |||
Full synthetic DEXRON VI distributed by General Motors and marketed as backward compatible with earlier DEXRON automatic transmissions. It tied the Mobil for the smallest wear scar at 8 mm, but it was the slowest fluid at -40°F both before and after heat exposure, and it gave up the most room-temperature flow speed after the heat cycle at 7.7 percent. | |||||
| Mobil | $13.00 | Search on Amazon | USA | ||
The only synthetic blend in the comparison, marketed on improved oxidation and thermal stability and optimized friction performance. It was the second-quickest fluid at -40°F and tied the AC Delco for the smallest wear scar at 8 mm, but it lost 20.61 grams to evaporation in the heat test. | |||||
Lower is better
Approximate price per quart at the time of testing.
Grams lost from a 200-gram sample — lower is better
Each fluid was weighed into a 200-gram sample, held at roughly 410°F for two hours, cooled, and weighed again. Red Line lost the least at 6.94 grams, with Super Tech and AC Delco close behind at 8.34 and 9.63. The Mobil synthetic blend lost 20.61 grams, more than twice what either full synthetic under $10 gave up, and darkened noticeably within the first twenty minutes.
| Rank | Product | Result |
|---|---|---|
| 1 | Red Line | 6.94 |
| 2 | Super Tech | 8.34 |
| 3 | AC Delco | 9.63 |
| 4 | Mobil | 20.61 |
Seconds to complete the -40°F flow course — lower is better
Fluid straight from the bottle, after ten hours in a freezer at -40°F. Red Line was first out of the gate and won by just over three inches, finishing in 24.53 seconds. The synthetic blend Mobil took second at 30.16, a gap of more than two inches over the two full synthetics, which came in around 34.5 seconds with Super Tech just edging out the AC Delco.
| Rank | Product | Result |
|---|---|---|
| 1 | Red Line | 24.53 |
| 2 | Mobil | 30.16 |
| 3 | Super Tech | 34.50 |
| 4 | AC Delco | 34.50 |
Seconds on the same -40°F course after two hours at 410°F — lower is better
Repeating the cold race with heat-cycled fluid separates durable additive packages from fragile ones. Red Line barely moved, going from 24.53 to 27.37 seconds, and widened its winning margin from three inches to five. The heat hit the Mobil hardest in relative terms — it slowed by 24.4 percent to 39.88 seconds and lost its clear advantage over the two full synthetics, while Super Tech slowed 14.2 percent and AC Delco 19 percent to finish last at 42.78.
| Rank | Product | Result |
|---|---|---|
| 1 | Red Line | 27.37 |
| 2 | Mobil | 39.88 |
| 3 | Super Tech | 40.14 |
| 4 | AC Delco | 42.78 |
Percentage of flow speed given up at about 70°F after two hours at 410°F — lower is better
At about 70°F all four fluids flow within a few hundredths of a second of one another when fresh, so the useful measurement is how much that changes once the fluid has been cooked. Red Line shifted least at 1.6 percent, followed by Mobil at 5.4, Super Tech at 7.1 and AC Delco at 7.7. A fluid that holds its viscosity is a fluid whose shift quality should stay closer to new for longer.
| Rank | Product | Result |
|---|---|---|
| 1 | Red Line | 1.60 |
| 2 | Mobil | 5.40 |
| 3 | Super Tech | 7.10 |
| 4 | AC Delco | 7.70 |
Red Line D6 ATF swept this comparison, taking first place in every category. It lost 6.94 grams to evaporation against 9.63 for the AC Delco and 20.61 for the Mobil, produced the smallest wear scar of the four, and covered the -40°F flow course in 24.53 seconds when the next-quickest fluid needed 30.16. It also degraded the least: after two hours at 410°F its cold-flow time slipped only 10.4 percent and its room-temperature flow speed only 1.6 percent. The lab analysis backs the bench results, with roughly two and a half times the anti-wear additive content of the other three and a detergent dispersant package above 300 parts per million.
At roughly a third of the price, Super Tech is the value pick, finishing second overall with an average finish of 2.8. It had the second-lowest evaporation loss at 8.34 grams and gave up only 14.2 percent of its cold-flow speed after the heat cycle, against 19 percent for the AC Delco and 24.4 percent for the Mobil. Its weak point is wear: at 8.44 mm its wear scar was the widest in the group, about five percent broader than the 8 mm the AC Delco and Mobil tied on.
The AC Delco is the cheapest quart here at about $8 and matched the Mobil for the smallest wear scar, but it was the slowest fluid at -40°F both before and after heat exposure. The Mobil is the one that needs the most thought: it is the only synthetic blend in the group, it flowed well cold when fresh and tied for the best wear result, but it lost 20.61 grams to evaporation and 24.4 percent of its cold-flow speed once heated — the worst result in the test on both counts. All four resisted foaming through a full five-minute shake, and all four started out with a total acid number under two, so the separation between them is about thermal durability and additive content rather than basic fitness for a DEXRON VI transmission.