Most engine manufacturers say 2010 will be like turning the clock back to the good old days

In 2002, diesels came with exhaust gas recirculation for the first time.

EGR put more stress on the engine, causing occasional failures of items like head gaskets and making the cooling system work a lot harder. EGR technology meant additional components like EGR valves and coolers and variable-geometry turbochargers that would occasionally fail. And it put a significant damper on fuel economy. Fuel usage increased because backpressure was needed in the exhaust system to drive exhaust back into the engine.

By 2006, the bugs with failed EGR valves and coolers and VG turbos were mostly a thing of the past. Engineers had even strengthened major internal parts to help guarantee durability. They recalibrated the ECM to meet the emissions standard while optimizing fuel economy. Thus, as 2007 approached, engines were running more reliably and had regained some of the lost fuel economy.

But 2007 brought increased levels of EGR to meet a still-lower NOx (oxides of nitrogen) standard and gave us the diesel particulate filter, or DPF, to meet a required significant drop in particulate from levels that already were very low. Lower-sulfur fuel, provided to cut particulate and preserve the DPF, together with the improved CJ-4 engine oil, meant better engine durability but more costly fuel and oil. In spite of increased EGR, engine-tuning tricks yielded fuel economy that was comparable with 2006 in most highway operations. But when the truck spends a lot of time under light load, a lot of fuel is used to regenerate the DPF. Also, at infrequent intervals, ash needs to be cleaned out of the DPF. All in all, not a pretty picture.

So what will 2010 bring? According to experts from most of the engine manufacturers, a breath of fresh air. It will be a lot like turning the clock back to the days before EGR became a factor.