Bro, on the accord, the fuel filter and the part connected to it had issues -- cost him about 1K to replace. The SC told him that this rarely happens, but more often who keep switching petrol brands. And for my cousin, he really doesn't care about what petrol he puts, every week, he puts whatever is on the way.

Part 2

Car: FD2, Yr 2007, 97K mileage. Driving with P3Drive setting of Eco 3.

Petronas
Consumption on Ron97 = 11.25 l/km or 18.2c/km @ today's prices
Consumption on Ron95 = 10.00 l/km or 19.2c/km @ today's prices

So, for me, Ron95 is more expensive. Noticibly, acceleration is not as smooth, and engine vibrates more

Caltex
Consumption on Ron95 = 10.89 l/km or 16.5c/km @ today's prices
I expect my consumption was higher this time due to having to keep the engine running for long hours due ICE tunings and ADAS competition
(used this petrol twice over 1.5 weeks). Will try Caltex 97 next week.

Switching from Petronas RON97 to Caltex RON95, I did not feel any drop in performance, and any increase in engine vibration. No difference at all.

I think I've proven that comparing petrol from different brands do not give a fair comparison of performance by RON ratings alone. Since all the marketing and hype go by RON ratings rather than brands ... it can be easily said by some who went from Petronas RON97 to Caltex RON95 that there is no drop in comsumption.

However, as some bros rightly pointed out, it may also depend on mods and the unique engine behaviour too. Just don't believe what marketing folks tell you.

Personally, got a bit drop in consumption l/km for RON95, but both given non significant total mileage different..meant example ~27.7 litre RON 95 and ~ 24.3 litre RON 97 , both pump in with RM 50 was exhibited same end total mileage .
However, RON 95 easy burn more fuel litre per/km compare RON97 for the same distance mileage, this is true as the fact that some extreme short hidrocarbon molekuo chain, multiple combustion in a sequence cylinder from initial extreme slight spark plug fire until full spark plug fire.
RON97 is more stable fuel, thus it's given more stable single combustion in a time especially for performance engine like FD2R, S2000 and other brand sport cars. If those performance car pump in RON95, the severe drop performance will feel due to multiple small burning sequences/knocking burn even it's still can run..

Personally, I feel the car become a bit heavy to accelerate from idle.
If you are cruishing along highway > 80 km/h, it don't feel the dragging much
For city ride , stop and go, it's pretty feel it for RON95, knocking burning and power won't accelerate as smooth as RON97.

Which one more easy to accumulate carbon oxide deposition on cylinder between RON95 a bit more foreign contaminants or RON97 in long run ? We should know the answer as nothing is same with different price of product.
Maintain the frequency of oil changed should be fine.

Part 3

Car: FD2, Yr 2007, 97K mileage. Driving with P3Drive setting of Eco 3.

Petronas
Consumption on Ron97 = 11.25 km/l or 18.2c/km @ today's prices
Consumption on Ron95 = 10.00 km/l or 19.2c/km @ today's prices

Noticibly, for RON 95 acceleration is not as smooth, and engine vibrates more

Caltex
Consumption on Ron97 = 11.01 km/l or 18.6c/km @ today's prices
Consumption on Ron95 = 10.89 km/l or 16.5c/km @ today's prices

No noticible difference in acceleration and/or engine vibrations between RON95 and RON97

Conclusion
With this, I end my personal journey of research. For my car, I can conclude that for any Petrol, Ron 95 gives poorer consumption to Ron97. For Caltex, however, I felt no drop of performance whatsoever between Ron95 and Ron97. However, the added benefit in consumption for Ron97 Caltex did not make the km/l any cheaper. The surprise here is Petronas 97 was better than Caltex 97, but no more better in performance compared to Caltex 95. So am sticking with Caltex Ron95 as it is had as good a performance as any of the Ron97s.

90% used RON95 n average filled RM20 (11.1 litres) or RM30 (16.7 litres)....90% used Esso/Mobil...10% used Shell...current FL1 mileage about 12k with 50% highway 50% city driving....

Esso:
RON95 got 130km (11.7km/l) to 145km (13.1km/l) for RM20
RON95 got 210km (12.6km/l) to 225km (13.5km/l) for RM30

Shell:
RON95 got 140km (12.6km/l) to 155km (14.0km/l) for RM20
RON95 got 220km (12.9km/l) to 235km (14.1km/l) for RM30

BHP:(Filled twice for RM20 each with 80% highway 20% city driving)
RON95 got 145km (13.1km/l) to 160km (14.4km/l)

Used BHP during Hari Raya Break...filled at Felda Gedangsa n managed to go Slim River using kampung road n returned back to Puchong thru Batang Berjuntai-Ijok-Puncak Alam-Shah Alam-Subang Jaya....

I believed Shell can give more mileage compare to Esso/Mobil.....try to use Caltex n BHP as Petronas gave me slightly lower fc compare to Esso/Mobil...

Still remembered filled in RM30 for Shell RON95 (80% highway 20% city driving).....from Puchong to Felda Gedangsa n returned back to Puchong by using same route...managed to clocked 205km 12.3km/l) eventhough high speed driving (175km/h++) just after UNISEL....

From my exprience,

RON 95 - less 10% mileage compare RON 97
RON 97 - Better power & mileage with additional 12% price compare RON 95.

Nothing same, you pay what you get.