Aston Martin Gear Oils
Gear oil selection is extremely important in an Aston martin. There are a few transmissions to take into account, so this page will detail information about the gear oils used in each. First is a quick overview of the transmissions, then a comparison of gear oils.
The transmission in the V8 Vantage is actually a transaxle - that is, it's a transmission and differential combined into one unit. So for this car, I often use "transmission" and "transaxle" interchangeably. For cars with transaxles, there is only one fluid used - both the transmission and differential share the same oil within the transaxle - so there is not a second gear oil to worry about.
This page is under construction and will continue to be updated and expanded.
Here's a quick video I shot during an obscenely hot day in my obscenely hot garage that quickly covers a few options:
6-Speed Manual Transaxle
Let's start off the with manual 6-speed transaxle in the V8 Vantage since it's the most likely to have non-OEM gear oil swapped into it. The current dealership fill is a special formula from Castrol called BOT 270A. This oil was developed to help alleviate stiff shifting when the transaxle is cold. It's essentially thinner while cold to let it flow easier before heating up - think of it as a 70w90. It helps with cold shifting, but it comes at a price: I've seen dealership prices range from $70 to $85 per liter. You need five of them to fill the transmission, so that's a good $350 or more in fluids alone!
The good news is that there are options if you want to save some cash by using a different gear oil. You can, technically, use any 75w90 GL-4 gear oil. However, keep in mind that all oils are different and each will have an effect on the gearbox. The most obvious difference will be that cold shifting issue - most gear oils are going to make the transmission difficult to shift until it warms up.
Something that won't be as obvious is how well the gear oil protects your transmission. Gear oil has two primary jobs: it lubricates the internals (gears, synchros, etc), and it protects them. Early GL-5 oils (those with additives to protect limited slip differentials) were corrosive to yellow metals, which are found in the synchros of a transmission. Newer GL-5 oils tend to be okay for yellow metals, but I don't recommend using a GL-5 oil in a transmission unless the technical data specifically states it is safe to do so.
Sport Shift Transmissions (ASM I/II/III)
The ASM transaxles are essentially the same as the manual ones, but they use robotic controls to change gears rather than the "stick" of the manual. Gear changes happen either automatically based on the transmission control unit (TCU) or by driver command via the shift paddles located behind the steering wheel.
Even though it's basically the same as the manual box, you should only use dealership-specific gear oil in the ASM. I have several customers that are using Motul Gear 300 in their ASM transmissions, but I tend to err on the side of caution and recommend sticking with the Castrol BOT270A gear oil in the SportShift gearbox.
The reason isn't because of a difference internally. Rather, it's because the system is tuned to expect a specific oil in the gearbox. The TCU expects a certain amount of compliance, resistance, and fluidity when moving gears, working the clutch, and so on. If that gear oil is changes, the parameters may not match up and yes, you can seriously damage your transmission.
Gear Oil Comparison
The main thing we want to look at in a comparison of high quality gear oils is the viscosity at two temperatures. This will tell us how fluid the gear oil is when cold and when hot. Cold temperature fluidity plays a huge role in shifting smoothness when you first start driving the car. It's a big deal for our transmissions - Aston has their own gear oil specification to alleviate this issue, and they revised the shifting mechanism as well.
Viscosities can vary wildly at different temperatures, so the Viscosity Index was created to give a rating for how much of a change there is for a given oil. As oil heats up, it gets more fluid and, conversely, as it cools it gets less fluid. The higher the Viscosity Index, the more consistent the fluidity across a range of temperatures.
Gear Oil Filtering
Like the other cycled fluids in your Aston Martin, the gear oil passes through a filter. The filter helps clean out contaminants so the oil can continue to function as efficiently as possible, and to collect any debris that may develop within the gearbox.
The filter itself is reusable. When you change your gear oil, it’s best to remove the filter and clean it, then reinstall it with a new o-ring. I sell Gear Oil Change packages that include this o-ring as well as the washers for the drain and fill plugs.