I finally got around to changing my manual transmission fluid in my Kia Soul, and I've noticed some interesting changes. I switched from the stock oil to Red Line MT-85 75W-85 Synthetic GL-4. I'm curious for input on my observations from the other gearheads on the forum.
First of all, the car already shifted smoothly in temperatures of around 0 F and higher. The main reason for the change was to reduce the stiffness in extreme cold weather, such as the -10 F days we had this past winter, when the stick was pretty stiff. Whether that objective was met will have to wait until winter.
Nonetheless, the stick does feel smoother now after having put about 75 miles on since the change. But the biggest difference is in the throw between the gears. It feels... dampened, for lack of a better word. It's kind of subjective, but it's real.
The biggest difference, however, has been the sound level. Previously the transaxle sounded like pretty much every other compact car manual transaxle I've ever driven, meaning that there was some synchro whine. I never considered it abnormal, nor did any mechanic or gearhead who drove the car. But now it's silent. I mean, we're talking silent. If I run over a leaf, I can hear it crunch. The tranny makes no noise.
In fact, I found myself shifting much later that I typically do because I'd been using the syncro whine as an aural shifting cue without really realizing it. Being kind of a hypermiler, on level ground I typically upshift at between 2,000 and 2,250 RPM. After the fluid swap, I found myself not shifting until as late as 3,000 RPM or more.
Another odd thing is that the car's upshift advice seems to be occuring a bit later, as well. I'm not quite sure about that, but prior to the change, when in ECO mode, the car would typically suggest upshifting at about 2,000 RPM on level ground. Now it seems closer to 2,500.
Another change that's definitely real is reduced deceleration due to engine braking. When you drive up and down the same mountains all the time, you get to know them pretty well and develop habits to maintain speed on the downhill sides.
On one downhill stretch that I drive very frequently, the speed limit drops from 55 at the top of the hill to 30 at the bottom. Previously, I could decelerate to about 35 by the time I got to the speed zone sign by shifting into fifth as I went over the crest, with neither gas nor brakes being needed from there until I reached the sign. Today I was at about 45 when I got to that sign.
The second hill is much longer but has a shallower incline, and a speed limit of 45 due to the many curves in the road. (45 really is about as fast as you'd want to drive on this stretch of road, by the way. It's pretty tortuous, and my county's not big on guardrails.) Previously I could take that hill at 45 by shifting into fifth at the top and applying a bit of gas here and there on the way down, but no brakes. Today I had to keep applying brakes to keep the speed under 50 and didn't have to give her gas at all.
I've noticed these kinds of changes in other cars when I swapped dino with synthetic, but never to the extent I'm noticing in this car. Some of it could be in my head, but the absence of synchro noise and the decreased deceleration due to engine braking most definitely are not.
I'm pretty glad I made the change, although winter will be the real test. I can't help but think that the elimination of any noise at all means better lubrication and longer gear and synchro life. But the other changes are just much more pronounced than I expected. Is this Red Line some sort of super oil? I'd frankly never heard of it before and only bought it because the folks on the Kia and Hyundai forums swear that it is THE oil for the companies' manual transaxles. Based on my impressions so far, I suspect that they're right.
Comments welcome. Thanks.
Rich
First of all, the car already shifted smoothly in temperatures of around 0 F and higher. The main reason for the change was to reduce the stiffness in extreme cold weather, such as the -10 F days we had this past winter, when the stick was pretty stiff. Whether that objective was met will have to wait until winter.
Nonetheless, the stick does feel smoother now after having put about 75 miles on since the change. But the biggest difference is in the throw between the gears. It feels... dampened, for lack of a better word. It's kind of subjective, but it's real.
The biggest difference, however, has been the sound level. Previously the transaxle sounded like pretty much every other compact car manual transaxle I've ever driven, meaning that there was some synchro whine. I never considered it abnormal, nor did any mechanic or gearhead who drove the car. But now it's silent. I mean, we're talking silent. If I run over a leaf, I can hear it crunch. The tranny makes no noise.
In fact, I found myself shifting much later that I typically do because I'd been using the syncro whine as an aural shifting cue without really realizing it. Being kind of a hypermiler, on level ground I typically upshift at between 2,000 and 2,250 RPM. After the fluid swap, I found myself not shifting until as late as 3,000 RPM or more.
Another odd thing is that the car's upshift advice seems to be occuring a bit later, as well. I'm not quite sure about that, but prior to the change, when in ECO mode, the car would typically suggest upshifting at about 2,000 RPM on level ground. Now it seems closer to 2,500.
Another change that's definitely real is reduced deceleration due to engine braking. When you drive up and down the same mountains all the time, you get to know them pretty well and develop habits to maintain speed on the downhill sides.
On one downhill stretch that I drive very frequently, the speed limit drops from 55 at the top of the hill to 30 at the bottom. Previously, I could decelerate to about 35 by the time I got to the speed zone sign by shifting into fifth as I went over the crest, with neither gas nor brakes being needed from there until I reached the sign. Today I was at about 45 when I got to that sign.
The second hill is much longer but has a shallower incline, and a speed limit of 45 due to the many curves in the road. (45 really is about as fast as you'd want to drive on this stretch of road, by the way. It's pretty tortuous, and my county's not big on guardrails.) Previously I could take that hill at 45 by shifting into fifth at the top and applying a bit of gas here and there on the way down, but no brakes. Today I had to keep applying brakes to keep the speed under 50 and didn't have to give her gas at all.
I've noticed these kinds of changes in other cars when I swapped dino with synthetic, but never to the extent I'm noticing in this car. Some of it could be in my head, but the absence of synchro noise and the decreased deceleration due to engine braking most definitely are not.
I'm pretty glad I made the change, although winter will be the real test. I can't help but think that the elimination of any noise at all means better lubrication and longer gear and synchro life. But the other changes are just much more pronounced than I expected. Is this Red Line some sort of super oil? I'd frankly never heard of it before and only bought it because the folks on the Kia and Hyundai forums swear that it is THE oil for the companies' manual transaxles. Based on my impressions so far, I suspect that they're right.
Comments welcome. Thanks.
Rich
Last edited:
