i have just read Dr Brace tips for fuel saving is thius what comes from a PHD scholer what a joke as if we dont know this already talk about stealing a living my 5 yeatr old daughter could have made those ground breaking discoverys they are all come sence motoring tips as old as the hills go and do something else you idiot

In my experience even main dealers are not always completely clued up where for instance on an electronic ignition system the agents suggested that I buy all the components and then tow the vehicle to a specialist about 80 miles away to have these fitted because this person was the only one who was qualified on these systems. It took me about 2 hours of fiddling to find and fix the fault

Mayfitz - can't see which one it is you mean at the moment, but I remember reading some fuel saving tips on here. Were those the ones suggesting to keep a petrol motor at between 2 and 3000rpm by any chance? My own fairly simplistic (but accurate enough to make the big indicated differences statistically sound) measurements have shown that to be false even. 1500rpm gets me noticably better economy than 2000, and keeping in high gear with as low a road speed as possible without labouring the motor (between 25 and 30mph in top for me - or 1200-1450rpm) gets the highest. Getting UP to 2000 in any gear is about the limit for not wasting serious amounts of fuel. I also take issue with the governmental recommendation to "change up at 2500rpm" for the same reason; I wouldn't be into FOURTH until I'd gone PAST 30mph under that scheme (and top at 40), wasting loads of fuel, and making tons of unneccessary noise and fumes, even though a typical modern petrol engine has plenty of give - certainly for low speed cruising - pretty much from idle. And unless you accelerate hard, or until you get up to speeds where wind resistance starts having a significant effect (over about 35mph), the main influence on the fuel consumption is the rpm (because of the rather high internal friction of an internal combustion engine - air pumping, compression, metal on metal in the cylinders, oil and water pumps, alternator, crankshaft and gearbox input shaft bearings, etc), and the throttle opening (a major baffle in the air intake... higher gears needing a wider open - and so less resistive - throttle to make the required power because of the lower rpm). The argument against is that this might not be good for the bearings, engine mounts, gaskets etc because of reduced oil flow and increased vibration, but with a light right foot and care taken to briefly shift down if stronger acceleartion / hill climbing is required I don't believe this will be a big problem (my last car was longer legged enough to virtually have an extra gear compared to this one, and ran from 25k thru to 65k miles in my care with quite a lot of in-city driving hitting top gear at ~33mph, was quite regularly serviced and the engine was still near-mint when it got run into and written off despite also being thrashed from time to time). Over-revving the engine for protracted periods with heavy throttle - and poor servicing - is more likely to cause issues... the only engine I've caused serious damage to came from it being regularly thrashed at high speed whilst having an undiagnosed thermostat fault. Conversely, they say to shift up at 2000 in diesels ... from my own experience driving the occasional day to day small to medium diesel or TDi van or car, this is also a bad idea. A light truck or an older non-turbo may be OK with it, but a turbo or a higher tuned, small displacement NA type won't like it. The motor will only just have properly come onto its torque band (where the efficiency zone is for a diesel) by 2000, and your first 2 changes (or 3 for a 6-speed), thanks to typically longer gears with wider gaps, will see your rpm drop far enough that even on full throttle there's almost no thrust left. Leaving you with a dangerous lack of acceleration, damaging judder, and possibly even stalling it when going into 2nd uphill (the Vaux Vectra is _terrible_ for this last one, as the clutch is also naff)... and not even improving your economy anyway. Sub-torque revs, though quieter, are only good with these engines for oiling along in a traffic queue. For proper performance, they need to spin a bit... they ACTUALLY give you a much better drive AND better economy if you stay in the 2000 - 3000 (3500 in 1st...) zone, so long as you don't boot the throttle all that hard, because you'll be seeing absolutely complete combustion. That's the nature of throttle-less, compression ignition engines (Getting the Vectra up to ~2500 in 6th gear, or about 75mph, still gave excellent economy). Quite where the quoted figures (whether 2000, 2500, or "2000-3000") come from is anyones guess, but I'm guessing its from the days of manually choked, carburetted, mechanical ignition, 8-valve, pushrod engines, with quite low gearing (eg 15mph/1000rpm)... where the imperfect engine running characteristics (not much to give between the sometimes quite high idle and the torque band, low peak power revs, narrow band of best torque and efficiency, etc) and peak torque almost exclusively falling somewhere in the mid to upper end of that 2-3k range would have actually made this true. It wasn't particularly true for my '91 Polo (simplistic but effective fuel injection, but otherwise stoneage and with low gears) even though it wasn't that powerful - still driveable and wonderfully efficient with 2000rpm upshifts, decidedly not so with the Astra that followed (similar tech but larger engine and much longer geared - 3000 usually felt like seriously over-revving it when not darting off the line), and demonstrably not the case in just a few short minutes with a fully "modern", all singing and dancing 16 valve turn-of-the-millennium Megane, with it's MPG reporting trip computer. Incidentally, there is a lower cutoff for efficiency - somewhere between 20 and 25mph for mine - for some reason. Definitely it starts getting thirstier again even well above idle (~15mph). Presumably even modern tech can't overcome the physical challenge of maintaining entirely complete and even combustion over the entire range from 750rpm up to its more modern peak torque point of 3750... But, it's still a great deal lower down the range than the official statements. I'd reckon you can knock 40% or maybe a little more off the govt. and "doctor" recommended figures to get the truly best results. Nothing wrong with all the other points, however - keeping the engine and car generally in good nick, keeping the tyres pumped (making sure of those two also means you're safer because of more regular checks) - though for ultimate economy, put them up a couple of PSI above the recommended level if you're also going to be keeping speeds down too, turning engine off at lights, *generally* changing up early (for safety's sake you sometimes have to ignore this!), emptying the boot, using the plain fan rather than either aircon or open windows, etc. They're merely the "same old thing" --- but I've seen for myself that some people STILL don't quite get the message until they see it for the 10th time, like here. Haven't been able to confirm how much difference gentle acceleration makes vs moderately strong (rather than all-out, which IS wasteful) but I suspect the improvement may be because your *average* road speed is lower. (I also coast engine-off down hills, but for legal reasons I can't recommend this and must say it's my own dangerous choice. Even though my steering at 40mph is no worse than in the non-PAS polo, there's plenty enough servo boost left in the brakes for an emergency stop, and after the initial key-off blip all other systems (guages, lights, ABS etc) still work fine, and if I do it with top gear still engaged and the clutch held down my ability to accelerate away in an emergency or apply engine braking is barely delayed by a quarter-second (no, bump starting in that way is no worse than going from over-run cutoff to normal running, or a slightly unskilled down shift from an imaginary 6th gear) :p ... and the benefit is palpable in the way that speed which would have been held steady or even gone down in the highest possible gear (requiring fuel input to stay constant), goes up by several mph instead, and the mpg meter steadily ticks up...:)

oh ffs. what is with the lack of newline spacing? please try to imagine that this post and the previous one have, like, paragraphs. because they were designed to...

tahrey you should write book well i think you just have nell

Jesus if that's what you call "car basics" no wonder women are ripped off. From a non-mechanic

tahrey: The best cruising speed is calculated so; 1/. Open the throttle wide as possible in neutral. This gives the maximum revs. 2/. List this on paper, then your most economic/efficient cruising speed is 66% of this for diesel (compression ignition), or 75% for spark ignition (petrol). We should normaly change up at this point on level ground, at lower speed downhill, sometimes even "block-changing", (skipping one or more cogs). We should obviously change up later, at higher speed, when driving uphill. We should change down at 33% or even less on level ground,with diesel, 25% or even less with petrol. We may even "block change" down, as above, downhill, more oft also uphill. Block changing saves work, clutch, transmissioin, chassis & suspension, also tyre wear. Wind resistance ("Cw") is not an issue below 50mph, at which point you may notice some loss of weight on the front axle (Weight Transfer), causing instability. Spoilers can reduce this. This will be 4x as bad with a trailer of equal weight! A thermostat defect would not go undiagnosed more than three minutes, as if it failed to open, it would overheat to a write off, blow steam & smoke in front of the screen less than 10 minutes after driving away from a cold start. A sticking thermostat was much more common in yesteryear, with pure tapwater, even worse in hard water areas. If jammed open, it would take an age to warm up, & cost more fuel in the process. You should not give up the day job just yet, you are obviously a brilliant sales engineer, an even better politician/civil servant. I only have 40 years in the transport industry, on road, rails, & tracks, through so many countries/continents, some weeks covering over 2,000 miles on heavy trucks, with no size/wieght limit. I spent a total of over 15 years as driving instructor C/D + E, for both the British, as also the German Dept of Transport (both direct), & also the German IRC.

you switch off your engine when traveling downhill? I think that says it all..... Owain

Being an engineer my self I have often wondered why so many vehicles are designed in such a way as to let you know only after an event like overheating, temp gauges etc are glanced at, but non of us drive with a constant eye on such things ,I started to design a unit with leds and an audible warning bleep (That can be over ridden) 6 lights all show greeen on starting , 1 oil level.2 oil temp,3 water level,4 water temp,5 brake fluid level and 6 a charge rate led indicator, if any one of the lights turn red it indicates a problem in the making as opposed to already having taken place and the audible bleep alerts the driver, all to often customers say I only saw the temp was high after it was too late, this unit could be stuck to the dash with double sided tape and wired directly to the battery and small sensors all as an after market add on ,ok new cars may have this all sown up, but youngsters like demon gimmicks but this I think is a practical idea?

My Mum took her car into her local dealer, they charged 10 pounds to change a light bulb, plus of course the cost of the bulb. Disgraceful, and that is the real problem. We have a Prime Minister who gets paid 194k a year, and then claims 75p for a bath plug. We are becoming a society consumed by greed. Whereby innocent consumers are regulated and bullied into the arms of legal fraudsters.