Fuel - Even though Leaded fuel has been unavailable in the UK for some time now, the question of the suitability of an engine for use with unleaded fuel still occurs from time to time. As most people are aware, the lead in fuel of the past, in addition to [providing improved “anti-knock” properties, also acted as a lubricant between the engine valves and seats. The uses of unleaded fuel therefore in an unsuitable engine can lead to premature valve failure, but exactly what engines can safely use it?

The requirement for unleaded fuel came about as a result of the fitment of catalytic converters. Early designs of converter would rapidly become restricted when the lead in fuel came in contact with the catalyst. Plugged converters became a very common problem in the UK in the mid to late 70's. Converters were first fitted to cars built to meet the California emissions standards for 1974. The remaining 49 states adopted them in 1975. Since the chances of finding a converter still being fitted to a 70's (or 80's) car is slim to none we need to look at the model year of the vehicle concerned. ANY American vehicle built for the 1975 model year (or later) will run on un-leaded fuel without modification. If a 1974 car is known to meet California standards this will be suitable too.

Another question which comes up quite frequently concerns the correct (and replacement) type of brake fluid that should be used in an American vehicle. Brake fluids are designed to meet US Department Of Transportation regulations. They are commonly referred to as DOT 3, 4 or 5.

All US manufacturers currently recommend DOT 3 fluid, so unless you are certain the fluid has been changed this should be your top-up. DOT 4 fluid is also a polyglycol fluid but does not mix well with DOT 3. Some fluids are designated as “compatible” with DOT 3 & DOT 4. This type therefore, can also be used for top up or fluid replacement.

DOT 5, however is a Silicone based fluid. It is incompatible with other types and can only be used in a braking system that has been thoroughly cleaned (or replaced). Its main advantage is that it is non-hygroscopic (does not absorb water) and thus can improve component life. Downsides include its slightly compressible, which can lead to a “spongy” brake pedal and a tendency to harbour small bubbles that can make bleeding difficult. It is not currently recommended by any US car maker and must never be used in vehicles equipped with ABS.

Seat Belts - People often think that the seat belt in their American car is broken (this foxes some MOT testers too, so it's worth remembering). People familiar with seat belts in European and Japanese vehicles know that when you tug on the belt it locks. This causes you to be held by the belt when the vehicle decelerates rapidly, but why does this not happen with most American belts? Basically there are two types of belts in common use today:-

Systems triggered by the belt's movement

Systems triggered by the car's movement



The central element of the first design is a centrifugal clutch. When the spool that holds the seat belt's webbing is rotated slowly, it moves freely. When it is pulled quickly, as a result of centrifugal force a weighted pivoting lever pushes on a cam piece which in turn causes a pawl to move that engages with teeth to lock the spool.

The second type as used by most American vehicles has a weighted pendulum at its core. When the car decelerates rapidly, inertia causes a pendulum to swing forward. The pawl on the other end of the pendulum catches hold of a ratchet gear attached to a spool which the belt is wound around. With the pawl gripping one of its teeth, the gear is unable to rotate anti-clockwise and neither can the spool connected to it ,thus holding the belt in tension and the occupant in place. Once the belt loosens again, the gear rotates clockwise and the pawl disengages.

Another common, yet surprising question is “How do I know if my car has ABS?”.

There are varying ABS systems in use and although fundamentally they all rely on modulation of hydraulic pressure, this is not always obvious. In addition to the master cylinder there will also be a valve/pump assembly mounted “downstream”. In the simplest case where only the rear wheels (RWABS) are monitored (mostly found on trucks and vans) the extra valve may not be seen.

The common denominator is the speed (wheel) sensor. Whatever system is used, electrical sensors will be found on the brake hubs or the rear axle (differential). The wiring is there for that sole purpose, so look out for it.