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Old 06-04-2013, 11:50 AM   #12 (permalink)
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Join Date: Aug 2012
Location: Grand Haven, MI
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Focus - '05 Ford Focus ZX3
90 day: 37 mpg (US)

The Ranger - '99 Ford F250 Superduty
90 day: 20.08 mpg (US)

The Prune - '09 Toyota Yaris
90 day: 43.89 mpg (US)
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Originally Posted by Diesel_Dave View Post
Each thermostat is different. Typically thermostats are specified by their crack open temp, i.e. a "190 deg stat" starts to open at 190 deg F. For most stats I've seen, full-open temp is ~20 deg F above the crack open temp.
Those numbers make sense. I removed my upper grill block yesterday to test a warm engine temperature difference from full grill block. My max operating temperature was ~20f higher than when thermostat would crack open.

Full grill block operating temp: normal range 200-214f; max 217f
Partial grill block (~70 square inch opening): normal range 172-176f; max 178f

Three important details I noticed:

1. Even with a full lower grill block my oil temperature barely approached a number that would open the thermostat.

2. The operating temperature dropped dramatically with just a minimal grill opening. It seems, for this Ford Focus at least, that a grill opening of ~20 square inches would allow sufficient cooling without operating fan.

3. For those of you running a grill block without a ScanGauge or Ultra Guage, be careful. Although the UltraGuage registered the full range of operating temperatures, my dashboard temperature gauge did not move noticeably (even while approaching 220f). Your in car temperature gauge may not tell the whole story; don't ruin your motor because of some stupid grill block.
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