Declining fuel economy and odd voltages
06-06-2024, 04:31 PM
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2022 GLA 200d
Declining fuel economy and odd voltages
I’ve had my 2022 200d for a bit over two years and 70,000 miles now (mostly highway/motorway, in E mode and on cruise control). For the first 23 months it was utterly predictable on fuel economy: 550 miles or so per tank. After 23 months, it started to decline and has been getting much worse.
History: up to 23 months - it would show fantastic fuel economy 90+% of the time and crap for about 20 mins every four-to-six hours of driving.
When looking at the engine data the crap fuel economy corresponded to showing 14.8v on the engine data and the good corresponded to showing 12.8v (that always seemed oddly low but was consistent - n.b. It still spiked to 14.8v when coasting downhill in ‘charge’ mode). The suggestion was that the high voltage and bad fuel economy corresponded to regen. Still, it averaged 59-60mpg in summer and 58 in winter.
After 23 months: Now we rarely manage to hit 500 miles per tank. Economy is down to 52mpg at best (40s now typical) and getting worse. The voltage shown is now never below 13.5V with the engine running and spends most of its time at 14.8v. Took it to the dealer and they “re-loaded the engine ecu software” saying that “it had just finished regen”. I know, it appeared to have been doing so for several thousand miles. The re-flash hasn’t helped and it’s just got worse in the last three weeks/2000 miles.
Have checked the tracking just to make sure we weren’t just scrubbing tyres but it really seems to be an engine issue. I was thinking injector issues or a false dpf regen signal.
I wondered what the hive mind might know what’s likely to be up? Is the voltage a red herring? It seems to correspond to worse fuel economy perfectly: 12.8v = excellent, 13.5V = poor, 14.8v awful.
History: up to 23 months - it would show fantastic fuel economy 90+% of the time and crap for about 20 mins every four-to-six hours of driving.
When looking at the engine data the crap fuel economy corresponded to showing 14.8v on the engine data and the good corresponded to showing 12.8v (that always seemed oddly low but was consistent - n.b. It still spiked to 14.8v when coasting downhill in ‘charge’ mode). The suggestion was that the high voltage and bad fuel economy corresponded to regen. Still, it averaged 59-60mpg in summer and 58 in winter.
After 23 months: Now we rarely manage to hit 500 miles per tank. Economy is down to 52mpg at best (40s now typical) and getting worse. The voltage shown is now never below 13.5V with the engine running and spends most of its time at 14.8v. Took it to the dealer and they “re-loaded the engine ecu software” saying that “it had just finished regen”. I know, it appeared to have been doing so for several thousand miles. The re-flash hasn’t helped and it’s just got worse in the last three weeks/2000 miles.
Have checked the tracking just to make sure we weren’t just scrubbing tyres but it really seems to be an engine issue. I was thinking injector issues or a false dpf regen signal.
I wondered what the hive mind might know what’s likely to be up? Is the voltage a red herring? It seems to correspond to worse fuel economy perfectly: 12.8v = excellent, 13.5V = poor, 14.8v awful.
