When Jim Roberts thinks about the coolant needs for engines compliant with the stricter 2007 and 2010 emissions regs, more questions than answers come to mind.

“It's a pretty challenging situation,” says Roberts, a technical service specialist with Shell Lubricants. “On the one hand, we know basically what the corrosion prevention requirements for 2007 and 2010 engines will be. On the other hand, we have no specs for the coolant per se for EGR engines or Caterpillar's ACERT systems in that timeframe. It's up to companies like Shell to work with engine [makers] and fleets to figure those needs out.”

Roberts notes that some of the basic changes that will affect engine coolant starting in ‘07 are fairly obvious. “For starters, we've seen some impact from the changes in ‘02. It was initially thought that bulk coolant temperatures would rise 20 to 30 deg. F,” he says. “Since ‘02, however, OEMs have changed the radiator size and increased coolant flow rates, which changed the coolant equation,” Roberts notes. “That's making things a little harder to calculate.”

In addition, he points out that EGR technology creates “hotspots” of extreme temperatures in some areas, notably where the ultra-hot exhaust gas is re-circulated, cooled down, and reintroduced into the engine. “Hotspots present an opportunity for engine coolant to degrade, since it is exposed to higher than normal heat levels,” Roberts explains. “It's a phenomenon we have to watch closely.”

“The whole key to coolant is that it helps the engine remove heat faster, protecting the vital components from heat-related stress and wear,” he says.

“We've seen that nitrite — the primary liner cavitation protective additive in conventional engine coolant — rapidly depletes in adverse conditions,” he says. “That may mean we have to adjust the maintenance interval for conventional engine coolant.”

There has also been talk of boosting and/or altering the nitrite additives to help them resist depletion caused by ‘07 and ‘10 engines, but unexpected side effects are a concern.

“Any new coolant we develop has to prove itself over hundreds of thousands of miles. Once engine OEMs approve it, they don't want to see it tweaked or altered in any fashion for fear of unintended side effects.”

Extended life engine coolants use a carboxylate additive technology that can protect all the different metals found in an engine, rather than a separate additive for each metal, which could create chemical imbalance complications.

“So if we get to 2007 or 2010 and a new metal is added to the engine for emission-reduction reasons, we have to make sure the coolant can protect it,” Roberts says, since different metals react differently to heat.

“Equally challenging are the higher and higher coolant flow rates being required to help remove the higher heat loads produced by these engines.”

Fleet needs also have to be factored in: engine coolant that performs better, lasts longer, and provides superior corrosion protection.

“Ultimately, what fleets want is a fill-for-life coolant — that maximizes simplicity for them,” says Roberts. “It certainly is an attainable goal, but the real problem is that the cooling system itself doesn't last forever and that the characteristics of 2007 and 2010 engines may affect coolant durability. You can't lock the coolant in there either; you have to be able to top it off as more heat is going to be transferred into the coolant, creating a variety of thermal stresses.”

What's most critical in developing coolants for ‘07-and ‘10-compliant engines is to ensure that they do what they're supposed to: handle the higher temperatures, prevent corrosion, and enable additive packages to hold up under the strain.

“When it comes down to it, fleets have to make sure they maintain their coolant — especially as we enter the 2007-2010 timeframe,” Roberts emphasizes. “Whether we shorten the drain interval or go to more durable, extended life formulations, it's vital to make sure that the engine coolant is doing its job.”