tyre inflators

[deggers316]

how accurate are the digital tyre inflators at forecourts,i set my tyres at 33lbs (from 30lbs) to go on a long motorway trip on thursday to-day when checking them (both barely warm on both occasions) they were all 29 lbs a loss all round of 4lbs ,in 4 days ? very odd

[AlBags]

I think 10-15% is not uncommon.
Temperature of the tyres when you check (and therefore pressure) can add to anomoly.