Frequently Asked Questions
Please be aware that these articles & guides are submitted by Forum and Club Members and experiences may vary. Always do your research and get a professional opinion.
If you would like to contribute to these FAQ, then dive in!
What fuel should I use?
As high an octane as possible - 98 octane should be the minimum! Japanese cars are designed and mapped to run on their 100 RON octane fuel. A lower octane rating can cause the engine to detonate/knock under load causing internal damage. In an ideal world the ECU will compensate for this using the knock sensor system but it is still far and away better to use the highest octane available. JDM models running standard ECUs will also make progressively more power with higher octane fuel up to 100RON For heavy abuse days such as dragstrip events, trackdays etc. it is worth considering running octane booster. While this will not generally produce more power from the engine it will provide an additional safety margin from detonation
How much fuel will it use?
The GT-Four is a performance 4wd car so do not expect great economy. Average on road figures for a standard car would probably work out around 22-27mpg. Those with a heavy right foot may struggle to even reach the lower end of this band. People with gentle right feet have been known to get 350+ miles out of a 13 gallon tank on long runs. So 30mpg is possible but not common! On track expect less than 10 mpg!
What engine oil should I use?
Brand choice is a very personal thing. Some owners use Castrol, some use Millers, some use Silkolene etc. etc. The Toyota recommendation is for a 10W50 multigrade. The important thing is that any turbo car should be using 100% synthetic oil to handle the extra heat generated by turbo applications. At the end of the day the choice is yours. Some people use cheap semi-synth and change it every couple of thousand miles with no apparent side effects
It is worth bearing in mind though that a couple of microns thickness of your engine oil is all that comes between the crankshaft spinning at 6000 rpm and the soft metal big end bearings!
Running in a new or rebuilt engine requires mineral or semi-synthetic oil for a limited mileage, usually between 500 and 1000 miles.
When should I change the oil?
It depends on the sort of use the car gets Turbo cars in general burn large amounts of fuel (in case you have not noticed!). This can lead to rapid contamination of engine oil with hydrocarbons
The general recommendation for "average" cars would be 3000 to 6000 miles of "average" use, however, those subjected to spirited use should aim for the lower end of that range and if the car is tracked or run up the dragstrip on a regular basis it might be a good idea to change it in between trackdays.
At the end of the day there are no hard and fast rules but as with choice of oil it is worth remembering that oil is the engine's blood.
What else should I change when changing the oil?
It is important that you also change the oil filter when replacing oil... If it has done it's job then the old filter will be full of particulate contaminates removed from the old oil. The last thing you want to do when putting fresh oil in is to run the risk of immediately contaminating it with this!
NB It is tempting to nip down to your local discount parts supplier and pick up the cheapest oil filter they have that will fit. This may be a false economy. The Toyota filter has an anti-drain valve to prevent all of the oil from draining out of the block when the engine is not running. In some cheaper filters this valve has been found wanting which could lead to short term oil starvation at startup. This should not be a problem with a genuine Toyota part. As with oil the choice is ultimately yours but bear in mind the oil system is the blood of your engine
What gearbox oil should I use?
Toyota specify a 75W90 GL5 gear oil. Again brand is a personal choice but as with engine oil you should be considering a fully synthetic oil only Ensure that you get GL-5 specification
The differential should hold around 5 litres.
Note Some users have experimented with ATF in worn gearboxes. This is an attempt to try and prolong it's life once it has begun to get crunchy on changes etc. While results on the whole have been neutral to positive you must be aware that by doing this you are working outside of the Toyota specified conditions and your results may be negative!
What is the wheel bolt pattern for my GT-Four?
What is the offset required when ordering aftermarket wheels?
Should I use spacers with my wheels?
For a simple quick start guide to wheels see the wheel information article
What is the standard boost on my car?
ST165 approximately up to 7psi
ST185 approximately up to 12psi
ST185 (CS/RC) approximately up to 12psi
ST205 approximately up to 14.7psi
What should I do before I start modifying the car
The first things aren’t really mods, more maintenance but are still recommended:
- Change engine oil and filter
- Check all fluid levels and rectify any leaks - brakes, clutch, engine coolant, IC coolant, gearbox oil, rear diff oil
- Change spark plugs
- Change leads
- Change rotor arm and dizzy cap
- Change the fuel filter
- Ensure the cambelt, power steering belt and alternator drive belts have all recently been changed
- Service or overhaul the brakes
In addition to the above, things that you could do that are free would be to;
- Remove under bonnet padding
- Remove resonator box from the inner wing
- Fit a cold air feed to the filter
What should be my first modifications?
Early modifications could include;
- Fitting a boost gauge (even a cheap is better than none! Budget boost gauges start at circa £35)
- Fitting a Relief Valve (Much better than a bleed valve) £15 from 
- Lag the charge cooler. Not a bhp gain as such but a good way of improving intercooler efficiency
- Fitting a replacement performance panel filter or similar
- Fitting colder grade spark plugs - BKR7E will be a fine replacement in all the GT4 engines
What Boost can I run with mild modifications?
With sensible "breathing and exhaling" mods you should be able to achieve:-
ST165 approximately up to 12psi *
ST185 approximately up to 12psi *
ST185 (CS/RC) approximately up to 14psi
ST205 approximately up to 17psi
* You will probably need a Fuel Cut defenser to achieve these figures