I must stand up here and say, in all truth and forthrightness, that during my watch at Motor Trend we NEVER faked a single road test performance chart.
Were we given ringer cars by the manufacturers? Probably all the time, unless it was a minivan, and even then probably so.
Car and Driver fudged their acceleration numbers without informing the readers, when they started in the 1990s subtracting a couple of tenths of a second off the actual e.t. to correspond with drag strip allowed roll-out, because the fifth wheel type of test equipment does not allow roll-out. Well that's definitely fudging/lying, in my opinion. At least say so in print, guys. Well, it took them over a decade to fess up.
I sent more than one test car back to the manufacturer, without writing about it, because it tested way too good compared with the previous year's version, despite no or very little change. Corvette ZR-1s were notorious for this. The variation in top speeds of five ZR-1 test cars (the "same" 405 hp engine car, over two model years) ranged between 167 and 182 mph. Something like: 167, 169, 171, 175, and 182. Same location and very similar weather conditions. Look-up Mrs Orcutt's Driveway. I was there and did a lot of the top speed driving. That proved to us the varying stages of wringers coming from Chevrolet. Plus, one of their guys admitted it privately to me.
He said "The other companies do it too."
Makes sense. When you're going to get publicity in any of the big three buff books (Automobile did not "test" cars, they "evaluated" them by driving to an expensive restaurant, followed by cognac and cigars) it makes sense that the companies would want to cheat, because they knew their competition were cheating. Just like in racing.
As a contrast to the above, I have a good buddy who works in the automotive division of Consumer Reports. Yeah, the magazine you check when you're buying a washing machine. Well, their car testing is more thorough and "honest" than any car magazine was or will be. Simply because CR BUYS all of their cars. NONE come from a Press Fleet or from a company engineering department. And they buy them from dealers all around the country, in the names of individuals, NOT as Consumer Reports.
They properly break-in each car for 2500 miles, set everything settable to factory specs, and then their cadre of white-jumpsuit drivers carry out the myriad tests back to back to back, to eliminate driver error and levels of skill. The test data is tabulated, and that's what they print. Sometimes, they'll keep a car for a year and retest it after the year's worth of miles, to see what's degraded.
It's a thorough testing regimen, but unfortunately their writing style is as boring to read as the recipe of how to make tofu mayonnaise. My buddy has to fight to get even one witty/funny/ironic line of text into any article he's writing. The big wigs in their gov't-like layers of management blue-pencil anything written with less than a "Robert's Rules of Order" type of pedantic structure, even if it makes no literal sense to change what the writer wrote. "Words by Alexa" is what it seems like they're after. But, their testing is truly top-notch.
As for the hot rod car mags like Hot Rod, Car Craft, PHR back in the day. They (I was there too) tested 1/4 mile times only. All they had was the timing clocks at a local drag strip. Only Motor Trend and the other big boys had fifth wheels.
Before those were invented, everyone used stopwatches operated by a passenger recording the times by watching the car's speedometer. THAT'S how Car and Driver got the laughable '65 Pontiac Catalina 2+2's 0-60 time of something like 4.5 seconds. Jim Wangers admitted later in life that not only did that car have a hand built and optimized engine, they changed the ring and pinion from the standard 3.0 (or whatever) to something like 3.90s. Gee, think that'll mess with the speedometer accuracy?
My main point in recounting this is that any test driver worth his magazine logo shirt can tell the difference between 0-60 in 4.5 seconds and 0-60 in 8.5 seconds. Yet, Car and Driver let it go to print. David E. probably got a free Bonneville, with a glove box full of cuban cigars, for that one.
And that's my .03 (adjusted for inflation.)