Is there a best time to change fluids? My thinking is that it is better to change atf/diff/transmission fluid before winter as the fluid has better cold properties when new. For coolant changing I believe its better to change before summer as thats when proper cooling is most important. Am i on the right train of thought here?
Change fluids before winter or before summer?
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I say change trans before the Summer heat because of it's higher level of new additives to better lubricate and change coolant before Winter for it's more robust anti-freeze properties.
Temperature cycles in the vehicle are deeper in the winter. This increases the likelihood of moisture in places it doesn't belong.
I tend to change gear oils in the middle of summer because that's when it's nicest outside to do such things
Same with brake fluid. I do oil changes staddling winter (fresh oil for winter protection, fresh oil after winter to get all the fuel, moisture and acid out).
Freeze and boil protection in coolant is based on the simple chemical property of it being an impurity in the water, as far as I know. I don't think coolant loses freeze/boil protection with age. It can become abrasive, promote electrolysis, and fail to protect against corrosion, however.
I try to get most things done before winter, because our winter is serious enough that I don't want to have something "come up" during winter that I have to fix when its -20, or resort to paying for labour instead of DIY.
I tend to change gear oils in the middle of summer because that's when it's nicest outside to do such things
Freeze and boil protection in coolant is based on the simple chemical property of it being an impurity in the water, as far as I know. I don't think coolant loses freeze/boil protection with age. It can become abrasive, promote electrolysis, and fail to protect against corrosion, however.
I try to get most things done before winter, because our winter is serious enough that I don't want to have something "come up" during winter that I have to fix when its -20, or resort to paying for labour instead of DIY.
If you believe that winter is harder on the fluids than summer (and my UOA's give compelling evidence that this is true) then it makes sense to me to change in the spring if you intend to do it once a year.
This way the fluid damaged by winter gets changed in spring, the clean fluid has an easy and unchallenging life through the summer, and is only in the gearbox (or whatever) for the 4 months of winter. This compared to having the beat-up fluid from winter in the sump all summer as well.
The former interval gives you 4 months on beat up fluid through the winter vs. 12 months on the beat up fluid (winter + summer).
This way the fluid damaged by winter gets changed in spring, the clean fluid has an easy and unchallenging life through the summer, and is only in the gearbox (or whatever) for the 4 months of winter. This compared to having the beat-up fluid from winter in the sump all summer as well.
The former interval gives you 4 months on beat up fluid through the winter vs. 12 months on the beat up fluid (winter + summer).
Yes. Change them before winter, or before summer. B~)
I guess it depends where you are from. Change them before winter if you are in Calgary and change them before summer if you are in Texas.
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I don't think it matters. Either way, it's not like you are completely wearing the fluid out before changing it (at least, you shouldn't be).
True for engine oils, but I've seen no evidence that cold weather affects gear and transmission oils as much as it does engine oils.
True for engine oils, but I've seen no evidence that cold weather affects gear and transmission oils as much as it does engine oils.
Originally Posted By: rpn453
I don't think it matters. Either way, it's not like you are completely wearing the fluid out before changing it (at least, you shouldn't be).
Quote:
If you believe that winter is harder on the fluids than summer (and my UOA's give compelling evidence that this is true) then it makes sense to me to change in the spring if you intend to do it once a year.
True for engine oils, but I've seen no evidence that cold weather affects gear and transmission oils as much as it does engine oils.
Fair enough, it might not be as much, however I would guess that in a cold climate the same rule would apply, just to a lesser extent as you have pointed out. For my money, I'd rather change after winter than before winter.
I don't think it matters. Either way, it's not like you are completely wearing the fluid out before changing it (at least, you shouldn't be).
Quote:
If you believe that winter is harder on the fluids than summer (and my UOA's give compelling evidence that this is true) then it makes sense to me to change in the spring if you intend to do it once a year.
True for engine oils, but I've seen no evidence that cold weather affects gear and transmission oils as much as it does engine oils.
Fair enough, it might not be as much, however I would guess that in a cold climate the same rule would apply, just to a lesser extent as you have pointed out. For my money, I'd rather change after winter than before winter.
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