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When to change the gear oil?

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Any advises on how often one need to change the gear oil for 2010, Mazda 3? Searched quite and most says never and that it cannot be possible to not to change gear oil - even if it's lifetime oil. Any help will be good here please. Thanks.

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HI Taqir, usually a German car brand claims the gear oil is for lifetime and what they mean is the lifetime of the gearbox which is close to 150k kms. In that case if you change gear oil after every 50k-60k kms you can happily use same gearbox close to 300k kms. This is what I realize and researched when I had ML350 in the past and had some gear oil leak.

For japanese, I would say same or slightly lower that you change gear oil at every 40k-50k km. Again this is just an educated guess. Are you sure you googled enough to find this actual number......?

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This is a very debatable topic as why so many car brands saying the same and then don't provide the dipstick in the engine bay and doesn't not include the gear-oil change frequency in the maintenance schedule.

On the second hand, why so many transmission repair shops now are busier in fixing the transmission than what they use to do 10 years back. Every transmission shop first opening question when you go for tranny problem: When have you last change the gear-oil. According to mechanics, heat build-up inside the gear-box is the main culprit for breaking the gear-box, as old, stale oil has become so thick that It doesn't provide any lubrication properties nor oil cooling properties to the gearbox and overtime gearbox dies.

My suggestion is to change the gear oil IMMEDIATELY even at the slightest doubt of gear jerking from 1st to 2nd (that's most noticeable). I ignored same in my Honda Accord in the past and went to shj for fixing with non-original parts for 2500 AED as original part fixing was 6000 dirham and new gearbox was 18000 dirham.

Changing gear oil is 200-300 dhs, so better change and be on safe side than not to change. My two cents.

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Hi taqir,

Unfortunately, there is no such thing as a "life-time" oil fill for any transmission, no matter what the manufacturer says.

Transmission fluid is no different from any other liquid lubricant, in the sense that it is a base oil to which several different types of additives are added to reduce friction, corrosion, and the formation of sludge. However, transmission fluid is not affected by oxidation as much engine oil is, but over time, the additives in transmission fluid will break down due to the effects of heat and contact with oxygen.

Nevertheless, high ambient temperatures, the effects of towing, and engine overheating are very difficult to quantify, so manufacturers base their claims of a "lifetime" oil fill for their transmissions on the supposition that the car will never be used for towing trailers and/or boats, that the engine will never overheat, and that the car will not be used in areas where  it gets very hot.

But this is only one half of the story. The other half involves the fact that modern transmisions are several times more complex than they were just ten years ago, so the reason why manufacturers do not provide dipsticks to check fluid levels is to prevent unskilled persons form tampering with the fluid level on the one hand, and to prevent people from adding the wrong fluid to a transmission, on the other hand. Most modern transmissions will only work with fluids that have been specifically designed for that specific transmission, and while most transmission fluids are red in colour, the wrong formulation can destroy a transmission. 

So, from a marketing perspective, it sounds great when a manufacturer says that the fluid never needs replacing, but from a practical standpoint, the transmission fluid cannot last forever. An added problem is that the amount of fluid some transmissions need are never published, so if you take the bull by the horns, and decide to replace the fluid in your transmission yourself, you don't know how much fluid will fill the transmission. Too much fluid is as bad as too little, so if you are experiencing trouble with a transmission that has a "lifetime" fill, the only place that can replace the fluid is the dealer, since you will often find that the transmission  fluid for your car is only available from the dealer.

My advice would be not to deal with independent transmission shops when you have problem with a transmission on which you cannot check, and adjust the level of the fluid yourself. Independents do not have the equipment to even check the fluid level, much less the diagnostic software to check for electronic causes of shifting problems. If your vehicle is still covered by a warranty, hold the dealer to his responsibility to fix all and any problems that you might have with the transmission.

Lastly, transmissions that have "lifetime" fills have no set fluid replacement intervals, but if you do a lot of towing, I would suggest you have the fluid replaced at the dealer at least once every two years. Towing raises the temperature of transmission fluid significantly, which causes the premature breakdown of the additives in the fluid.

I hope this helps, but if you have further questions or concerns, let me know.




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