Diesel Servicing in Redwood City: Fuel, Filters and Smoke

A diesel lights its fuel by squeezing air until it's hot enough to do the job on its own. No spark, no coil, no distributor.

Compression is far higher than on a gas engine, injection pressures are extreme, and the tolerances inside a diesel injector are very fine indeed.

So the maintenance burden shifts. Almost all of it lands on the fuel side and the emissions side, and there's more of it there than a gas engine ever asks for.

Short local trips are the hard case for a modern diesel. A particulate filter needs sustained higher-temperature running to burn off the soot it collects. A vehicle that only ever does short trips around town never gets the chance, so the filter gradually blocks.

Contaminated fuel doesn't damage a diesel slowly. It damages the two most expensive parts in the fuel system.

The high pressure pump and the injectors are machined to tolerances where a particle you can barely see behaves like an abrasive.

Water is worse than dirt, because diesel fuel is also the lubricant inside those components and water is the opposite of one.

That's why a diesel filter is changed more often than a gas one, and why it usually has a water separator built in or sitting beside it. It's the cheapest protection on the vehicle.

A diesel particulate filter traps soot and then has to get rid of it, which it does by burning it off. That needs sustained heat in the exhaust.

The vehicle manages that process itself when the conditions allow. What it can't do is create the conditions.

A diesel that only does short local runs never gets the exhaust hot enough for long enough. Every trip adds soot and none of it comes back out, so the filter gradually blocks and a warning light eventually arrives.

If that describes how your vehicle gets used, it's much better to know early than to find out from the dashboard.

Contaminated fuel doesn't damage a diesel slowly. It damages the two most expensive parts in the fuel system.

Want it checked? Describe what the car is doing and Five Points Tire will tell you whether it needs diesel servicing or something else. Call 650-365-0280, or send the form and someone calls you back. Request an appointment

A cold diesel needs help. Glow plugs preheat the combustion chamber so the compressed air is hot enough to light the fuel on the first turn.

They fail one at a time, which is why the complaint arrives so gradually. One gone and it cranks a little longer on a cold morning. Two or three gone and it takes several attempts, or waits until the afternoon.

The signature is precise and worth recognizing. Cold starting gets steadily worse while warm starting stays completely normal.

Battery condition and fuel supply cause hard starting too, so it gets checked rather than assumed. But that pattern points at glow plugs first.

Two identical trucks, same year, same odometer reading, can need noticeably different service schedules.

One tows a loaded trailer up grades at weekends. The other does a four-mile commute. The first is working the fuel system, the cooling system and the oil hard. The second barely gets the exhaust warm.

Both are harder on the engine than steady freeway miles, in opposite directions, and neither is described by the odometer.

So we service diesels against the make, model, usage and mileage of the specific vehicle, and we can tell you what the manufacturer asks for yours.

Keep the fuel filter on schedule, and drain the water separator if yours has one. That's most of the job done.

If the vehicle lives on short trips, plan around the particulate filter rather than waiting for the light.

Note the color of any smoke and when it appears, and note whether hard starting is cold only. Both narrow it down before we start.

Tell Five Points Tire the make, model and how you use it on 650-365-0280. A truck that tows all day and one that idles around town need different intervals.