Did the tire size change at all?

I've heard some tires being advertized as fuel saving (specific patterns reducing resistance, etc) but surely not to that much difference.

Maybe alignment isn't done correctly. Either too much toe-in or toe-out which explains why your car feels under power and you're getting less mileage.

https://www.quora.com/How-is-toe-in-toe-out...-in-automobiles

Are the new tyres more grippier than the previous set?

Higher traction tyres can increase a bit fuel consumption.

Trade off for better road handling performance.

OK.... from what tire to what tire (brand/series)

Amount of air pressure. The more rubber sticks to the floor the more power you need and more traction.

Different series different brand has different tire characteristic. Some tires have softer sidewall and some harder. Even if you put same air pressure, the one with softer sidewall will bulge more thus the overall diameter of the tire is less than the harder sidewall.

With smaller diameter, the tires need more rotation to go the same distance compare to the other tires leading to more fuel used. The more contact, the harder to roll, adding another factor. Another possibility is that you are comparing your old end of life tire with new one.. The old tires lost probably about 2.5 cm of radius, thus this contributes to at lease 3% of fuel consumption increment. 

cannot be tyre problem. even if you change 2 size up it wont be so much difference.

interesting, but I think you now had to make more funds to change to another brand?

I have the same feeling. I just change few days ago. New tire feel softer but heavier.

Maybe is just too new and the air pressure different. I increase a bit more pressure to get back my feel.

I am not sure if lesser known brands or tyre size can increase fuel consumption until almost 30%.

Unless those tires are really heavy increasing your unsprung weight + tyre pressure + ineffective traction.

If this is the case then saving on cost of tyre is really not effective as the consumption is up by 30% and multiply that by 2-3 years of lifespan. You will be paying more.

Ugh unknown China cheapo brand but nonetheless should not cause such drastic drop in fuel consumption.  I suggest you recheck the tire pressure yourself at the fuel station then observe again for several rounds of full tank (not just simply fill up rm50). Measure properly by resetting the trip meter to zero everytime you pump full then drive until fuel warning light turn on then see how far you travel. My suspicion is tire pressure too low and you didn't measure properly but just by feel which is inaccurate.

Btw what car do you drive, what tire size and how much did you pay for that China cheapo tires??

I will say is personal preference and depends on pump at Petro Station. You will find out you pump same psi but different pump different result.

Personally i pump up to 34 psi front, 31 psi back, way higher than 200. 200 is soft and conform, but for my car (old Persona) is just too heavy.

I would say you can increase a bit first maybe 220 kpa, then try few days if not enough increase to 230, 240 until you find the pressure you like. But of couse don't exceed the maximum pressure as listed on the tyre, which i don't think so, as most tyre maximum pressure is above 40 psi.

Good luck, bro.

old tayar botak, botak less grip, less grip means less friction, less friction means care use less petrol to move.. on the flip side, less grip means higher chance of accident on wet road

200 or 220 is a bit too low for most typical passenger car tyres , more so if fuel consumption or sluggishness is of concern to you .

Give yourself up to 260-280 to 'feel' the improved fuel economy , never mind tyre brands .

Welcome, bro. You may try up to 260 or above as per zeng mentioned. Until you feel too bumpy then just reduce a bit, that should be the best then.

My is 2011 Persona

Wah really damn cheap, scary cheap almost like used tire price. I personally would rather buy used tires but good ones than these unknown cheapo but most people don't know how to check hence not an option for them. Anyway understandable in this difficult times, many loose jobs or get pay cuts so need to try save as much as possible. Just be mindful when driving coz usually these cheapo tires have horrendous grip especially in the wet. Drive safe.
No lah, most car std recommended pressure is around 190-230. My Evo and Swift only 220 front and 200 rear. My heavy Mark X only 230-240 max. 260-280 is already too hard for most cars unless you like harsh uncomfortable ride. Too high pressure like that also lose grip and too nervous in the wet. Persona is also a light car, no need such high pressures, at most should be just 220-230.