Can someone tell me whether the fuel consumption degrades over the years ? For an example, I have a 2012 Prius (3rd Gen) and it's not doing good as it used to be (even after a injector clean up). My serviceman says this is typical behavior for Prius. I used to do 700KM+ with one full tank and I am not doing only 500KM+
no, it doesn't generally degrade. but when it does, it simply means some part(s) of your car are worn/dirty, and not performing as new. unfortunately, finding the culprits can be like the proverbial needle in a haystack.
How many miles on it? As the miles pile up, usually the ice gets clogged with carbon and can reduce efficiency. What type of fuel (top tier or what is available when you need it)? Do you use fuel injector cleaners? Just done the maintenance schedule in the owners manual or any other servicing ( PCV valve, etc). Have you seen any lights on the dash? Has your driving route changed? These questions will help with diagnosis and help with finding that small needle @bisco is talking about. Good luck!
tire pressure, 12v battery, oil overfill, pcv, plugs, egr and intake manifold, brakes rubbing or bad wheel bearing, parking brake rubbing, alignment, injectors, there are probably others as well. you also need to look at external factors such as weather, driving habits, gas formulation and etc. there's a good gen 2 sticky with a questionnaire if you're concerned about mpg's.
EGR clogging seems to one of the third gen "facts of life", somewhere between 100~150K miles carbon build-up gets bad. Not sure of the consequence, but I believe it degrades mpg. If it's really bad a warning light comes up though.
Although not a Prius I threw in a bottle of Techron and ran a few tanks of Shell V Power through my 97 Volvo 960 118K and saw an increase of around 10% in my highway mileage. The car use to get 29.25-29.75 mpg on the highway and slowly over the last six or seven years dropped into the high 26's. Yes I ran the cheapest premium I could find when I drove the car. I had it out a few weeks ago for a trip across the state and after a little over two tanks of Shell V Power and the bottle of Techron I saw an average of 29.2 mpg, and when I turned on the AC it only dropped to 28.5. That is far better than <27 mpg's I was getting with no A/C. I use to wonder why in the years past at least once a year when I had my Volvo's dealer serviced, the dealer would throw in a can of BG 44K into the gas tank. BTW they say that BG 44K is the best fuel system cleaner you can buy. The Prius runs on regular but a fuel system treatment once or twice a year plus running top tier gas may help improve your fuel mileage. I was starting to see a slight drop in fuel mileage in my Prius also (62K miles). I started running top tier fuel in the Prius over the last three or four tanks and this present tank I added a bottle of Techron. So far it looks like the fuel mileage may have improved slightly according to my Scan Gauge. Although I'll have to see over the long term to be sure. Lucky for me the Top Tier stations around me are selling gas for the same price as the off brand stations. Wayne Gerdes did a five thousand mile comparison run with specially modified six cylinder Dodge Charger which had dual fuel tanks feeding separate banks of cylinders for Shell. One side was fed Shell V Power + Nitro and the other a well known brand after the five thousand miles Shell tore down the engine. The intake valves told the story of which fuel actually kept the engine clean. You can look the story up on the Net or Youtube. After what happened with my Volvo and changing over to top tier nothing but the good stuff for now on.
I put a partial can of 44K in my 2010 Prius II ( it treats 20 gallons so I put the remainder in the wife's 4Runner. I noticed about the same increase in fuel economy in both cars you saw in the Volvo. Before the last oil change I also put in a can of BG EPR due to fuel economy and oil consumption. The EPR did cleanse the system (the oil came out jet black). I have put about 1,200 miles on the Prius since treatment. The last tank of gas I got 52 mpg, where the average over the last 58 k miles was 47 mpg. BG Products makes some good stuff.
Both cars come up for oil changes in December so I'm planning on doing a BG EPR oil service to finish up cleaning up the engine. Hopefully I can maximize the fuel mileage in both vehicles.
In the 1200 miles since the EPR treatment, the oil consumption has also gone down. It has only dropped about 1/8 of an inch from the top dot. This should equate to about 2-3 ounces. In your post above, I saw you were at 62 k miles on your Prius. Or is it more now? I also have been trying to use more top tier gas (Arco out here is relatively the same cost as the mom and pops excluding the fee for using a debit card). My plan is to also use the EPR treatment on the wife's 98 4Runner with 255 k miles and counting. Absolutely zero oil consumption but mpg keeps dropping. She does more around town errand running, but seeing the steady decline. The EPR treatment has been successful so far. I know @farmecologist also did one recently, but he is also very short mileage into his for definitive effects. Keep us posted.
The Prius has something like 62,3XX on the odometer. I've seen zero oil use so far with 4,500 mile OCI The Volvo on the other hand is a different story. Speed kills fuel mileage and burns lots of oil. Difference between the speed limit 70 mph and running at a max of 65 mph is three mpg and a quart of oil over 1170 miles. At a max of 65 mph on a round trip of 2340 miles I might go through a 1/2 quart of Mobil One 10W30. Obviously an EPR treatment is going to help the Volvo.
Agreed on the elevated speed. On the west coast we do the run from the Bay Area to southern Cali at least twice a year. On that trip we go 75- 80 mph average ( with speeds often exceeding 80 mph). When I check the dipstick, the level drops faster. A round trip of about 900 miles will go through a little over 1/2 quart of oil. Normal commute driving at 65-70 mph is where consumption declines in my case to what is normal. But the EPR seems to have reduced the consumption level so far . Good luck with the Volvo. I see you have Pittsburgh as your location. Life long Steeler, Pirates and Penguins fan here. Saw the score from yesterday's Steelers game and was in disbelief. Didn't get a chance to watch it( they had the colts chargers game on out here).
LOL. My old man was out here this weekend ( I am originally from NE Pennsylvania) and if the game was on, we would have been saying the same thing at the TV! Maybe I will have to get my Super bowl XL DVD fired up today.
