Modern fluids vs Old car Options

[Andre_L]

Hey, I'm a new owner of an ST204, and I was wondering when adding and/or changing the fluids should I keep to the fluids recommended in the owner's manual, or if there are better modern solutions considering the age of the car? I'm talking everything: oil, trans, brake, coolant, etc. The reason I bring this up is because I want to change the oil, and I read somewhere that it's not recommended to use full synthetic, however if the car has already been given synthetic then it's ok. Unfortunately I forgot to ask the previous owner a lot of important questions, so I don't know if it has been given synthetic.

Any input and responses are greatly appreciated.

[Bitter]

Use synthetic, if it leaks after it's because things were in bad shape anyway and were going to leak anyway. Change the fluids, not doing so is more harmful.

[Andre_L]

Use synthetic, if it leaks after it's because things were in bad shape anyway and were going to leak anyway. Change the fluids, not doing so is more harmful.

Alright, use synthetic noted. What about the other fluids? Use the recommended in the manual or is there something better?

[Bitter]

Better is usually better, as long as the new fluids meet or exceed the specs denoted. Dot4 is an upgrade from Dot3, gear oils can be tricky though, some don't work well in some transmissions or with worn transmission, and some make a worn transmission feel new again. Powersteering fluid can be swapped out for synthetic auto trans fluid to improve cold weather performance.

[nics]

Use synthetic, if it leaks after it's because things were in bad shape anyway and were going to leak anyway. Change the fluids, not doing so is more harmful.

Alright, use synthetic noted. What about the other fluids? Use the recommended in the manual or is there something better?

Like what Bitter said, synthetic is better but stick to recommended OCI.

Taken from Mobil1:

Mobil 1 High Mileage - synthetic
If you’re unsure about the maintenance history of your vehicle, then Mobil 1™ High Mileage synthetic motor oil is the best choice. Why? This high mileage oil contains a higher base oil viscosity to help reduce leaks and provide better high temperature protection. Mobil 1 High Mileage also provides unsurpassed wear protection of critical engine components. Plus, if your engine contains excessive sludge deposits due to less-than-adequate maintenance practices, this high mileage oil can help by reducing this sludge.

Mobil Super High Mileage - synthetic blend
If you know your vehicle has received regular oil changes at the manufacturer’s suggested intervals, then Mobil Super™ High Mileage conventional motor oil is a great choice. Why? This high mileage oil contains seal conditioners to help prevent leaks and control oil consumption.

Keeping your vehicle well maintained and running smoothly is the key to a longer lasting engine. And as drivers hang on to their aging cars and trucks, perhaps much longer than originally planned, it becomes even more important to give them the care they need. Your older engine might require you to spend more time in the driveway with your hood propped up, but your careful attention can add many more miles to your vehicle’s life, even well into its senior years.

I've been using Castrol High Mileage gtx (synthetic blend), OCI at 4k miles with seafoam treatment - engine at 338K miles


Oh and I just found out that when I had my axles replaced, my tranny has been running on 10w-30 until now. I haven't bothered to change it back to 75w-90 - don't do this

[Andre_L]

Alright cool, thanks guys. I'll be picking up the Mobil 1 High Mileage oil, and get the next DOT up.