To a point yes it can. The basic dynamics of the car are fixed but the balance in it can be altered and therefore the feel and responsiveness is changed as a result!
The oil in a 911 is checked when the engine is at normal operating temperature, after it has been idling for approximately 2 minutes. The dip stick is found in the engine compartment in the RH corner, under the filler cap inside the inner mudguard. The oil should be just under the second or top mark on the dip stick. The oil level gauge, on the dash is for an indication only and should be used to confirm the level.
In the great majority of times it is difficult to do this as many of the cars I work on are pre 1990, as a result of that they have all different histories. A lot of the time there has been accident damage, rust, seized fasteners or bad repairs that need to be overcome. So at best I can give an estimate and keep in touch with the customer as the job progresses.
Yes we do communicate with the client about any additional work. This is something we pride ourselves on. The only time this does not happen is when the item required is very minor and this is usually included in the price of the job. The only additional cost to the client is normally the part it self if required.
Well this depends on your car and use. A performance car or most modern cars with high compression, will almost without doubt run best in every way with 98 octane fuel! As a bonus to that an improvement in throttle response and fuel economy will be found. Generally any of Mechanical Fuel Injection or Carburettor 911's will be far better on 98 octane!
This depends on the type of use the car gets. If it does very few Kms each year then it is advisable to change the oil every year to remove any condensation engine and oil system. if a normal mix of city and country kms is the use, then every 10,000 km for semi synthetic oils and 15,000km! With fast road and track use, 10000 kms is the maximum! Pure race Kms oil changes should be a maximum every second race meeting!
This can be done easily, I have done this a number of times before with careful selection of components, and procedures
Fuel filters should be replaced annually at a minimum. if you are doing above 20,000 Km per year then every 15,000 to 20,000 Kms. Fuel quality these days is not as good as we are told, the dirt and rubbish that comes out of fuel systems is frightening at times, and the number of blocked fuel filters is staggering these days!
In many cases no. I often discuss and plan with a client to group sections of work that is required. If a car needs a lot of work we will often do related items together then re visit remaining work later.