new fuel injectors to improve MPG after 100K?

It would be good if they posted a PDF of the install instruction. See what you're in for.

 

That's an interesting question Doc Willie. Now I'm starting to wonder if it's time to replace the injectors. I have 160,000+ miles and I'm use to getting 52 mpg, but I've only been getting 45 - 48 mpg. I don't know if its all in my head, as in I use to drive slower and get stuck in more traffic jambs which would yield higher mpg, now I'm finding myself driving faster and avoiding traffic, so maybe that's the reason for less mpg?

I just bought a can of Royal Purple Max-Clean hoping to regain some fuel economy, but we'll see... Max-Clean Fuel System Cleaner for Maximum Fuel System Performance | Royal Purple

When do you think the injectors should be replaced?

 

When they fail. Loss of fuel efficiency usually is not a result of defective injectors. And changing out a perfectly good injector will not help anything except the profit of the company selling them. More marketing snake oil.

 

So is there a threshold fuel trim where it is logical to conclude they have failed (assuming spark plugs are not old and are properly gapped)? (Edit: there are a lot of other rule outs before injectors, especially vacuum leaks.)

Getting them professionally tested likely costs almost as much as buying replacements, so is there an easy way to tell they are bad? Long term fuel trim is an xguage readout on the scanguage and mine shows less than three on both my 06 and 08 so I think mine are fine. I've heard that the CEL comes on at 20, but perhaps numbers greater than 10 might indicate a problem that hasn't progressed to the point of throwing a code. In that case I'd say replace spark plugs first, then fuel injectors if the fuel trim doesn't improve .

On a similar note, I think a charge state differential of 0.0 is indicative of a healthy traction battery, but I'm not sure what threshold number above 0.0 would be considered time to start shopping for hybrid battery cells before you get stranded. Perhaps 7% but that's speculative.